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-rw-r--r--README.markdown1
-rw-r--r--c.html.markdown41
-rw-r--r--clojure.html.markdown102
-rw-r--r--dart.html.markdown5
-rw-r--r--elixir.html.markdown398
-rw-r--r--erlang.html.markdown239
-rw-r--r--file.erb1
-rw-r--r--fsharp.html.markdown5
-rw-r--r--haskell.html.markdown188
-rw-r--r--java.html.markdown407
-rw-r--r--javascript.html.markdown433
-rw-r--r--julia.html.markdown525
-rw-r--r--lua.html.markdown5
-rw-r--r--php.html.markdown232
-rw-r--r--python.html.markdown129
-rw-r--r--r.html.markdown86
-rw-r--r--ruby.html.markdown313
17 files changed, 2903 insertions, 207 deletions
diff --git a/README.markdown b/README.markdown
index 3223a2bd..77e09abd 100644
--- a/README.markdown
+++ b/README.markdown
@@ -17,7 +17,6 @@ properly!
The most requested languages are:
* Scala
-* Python
* Javascript
... but there are many more requests to do "every language", so don't let that stop you.
diff --git a/c.html.markdown b/c.html.markdown
index f2b9047b..132f75dc 100644
--- a/c.html.markdown
+++ b/c.html.markdown
@@ -1,7 +1,8 @@
---
language: c
-author: Adam Bard
-author_url: http://adambard.com/
+filename: learnc.c
+contributors:
+ - ["Adam Bard", "http://adambard.com/"]
---
Ah, C. Still the language of modern high-performance computing.
@@ -12,6 +13,7 @@ memory management and C will take you as far as you need to go.
```c
// Single-line comments start with //
+
/*
Multi-line comments look like this.
*/
@@ -19,6 +21,7 @@ Multi-line comments look like this.
// Import headers with #include
#include <stdlib.h>
#include <stdio.h>
+#include <string.h>
// Declare function signatures in advance in a .h file, or at the top of
// your .c file.
@@ -75,7 +78,7 @@ unsigned long long ux_long_long;
// on your machine. sizeof(T) gives you the size of a variable with type T in
// bytes so you can express the size of these types in a portable way.
// For example,
-printf("%d\n", sizeof(int)); // => 4 (on machines with 4-byte words)
+printf("%lu\n", sizeof(int)); // => 4 (on machines with 4-byte words)
// Arrays must be initialized with a concrete size.
char my_char_array[20]; // This array occupies 1 * 20 = 20 bytes
@@ -107,7 +110,7 @@ Char #17 is the NUL byte.
Chars #18, 19 and 20 have undefined values.
*/
-printf("%d\n", a_string[16]); => 0
+printf("%d\n", a_string[16]); // => 0
///////////////////////////////////////
// Operators
@@ -360,6 +363,36 @@ int area(rect r){
return r.width * r.height;
}
+///////////////////////////////////////
+// Function pointers
+///////////////////////////////////////
+/*
+At runtime, functions are located at known memory addresses. Function pointers are
+much likely any other pointer (they just store a memory address), but can be used
+to invoke functions directly, and to pass handlers (or callback functions) around.
+However, definition syntax may be initially confusing.
+
+Example: use str_reverse from a pointer
+*/
+void str_reverse_through_pointer(char * str_in) {
+ // Define a function pointer variable, named f.
+ void (*f)(char *); // Signature should exactly match the target function.
+ f = &str_reverse; // Assign the address for the actual function (determined at runtime)
+ (*f)(str_in); // Just calling the function through the pointer
+ // f(str_in); // That's an alternative but equally valid syntax for calling it.
+}
+
+/*
+As long as function signatures match, you can assign any function to the same pointer.
+Function pointers are usually typedef'd for simplicity and readability, as follows:
+*/
+
+typedef void (*my_fnp_type)(char *);
+
+// The used when declaring the actual pointer variable:
+// ...
+// my_fnp_type f;
+
```
## Further Reading
diff --git a/clojure.html.markdown b/clojure.html.markdown
index 24250a87..6baae0ce 100644
--- a/clojure.html.markdown
+++ b/clojure.html.markdown
@@ -1,10 +1,11 @@
---
language: clojure
-author: Adam Bard
-author_url: http://adambard.com/
+filename: learnclojure.clj
+contributors:
+ - ["Adam Bard", "http://adambard.com/"]
---
-Clojure is a variant of LISP developed for the Java Virtual Machine. It has
+Clojure is a Lisp family language developed for the Java Virtual Machine. It has
a much stronger emphasis on pure [functional programming](https://en.wikipedia.org/wiki/Functional_programming) than
Common Lisp, but includes several [STM](https://en.wikipedia.org/wiki/Software_transactional_memory) utilities to handle
state as it comes up.
@@ -23,9 +24,9 @@ and often automatically.
;
; The clojure reader assumes that the first thing is a
; function or macro to call, and the rest are arguments.
-;
-; Here's a function that sets the current namespace:
-(ns test)
+
+; The first call in a file should be ns, to set the namespace
+(ns learnclojure)
; More basic examples:
@@ -59,15 +60,18 @@ and often automatically.
(class false) ; Booleans are java.lang.Boolean
(class nil); The "null" value is called nil
-; If you want to create a literal list of data, use ' to make a "symbol"
+; If you want to create a literal list of data, use ' to stop it from
+; being evaluated
'(+ 1 2) ; => (+ 1 2)
+; (shorthand for (quote (+ 1 2))
-; You can eval symbols.
+; You can eval a quoted list
(eval '(+ 1 2)) ; => 3
; Collections & Sequences
;;;;;;;;;;;;;;;;;;;
+; Lists are linked-list data structures, while Vectors are array-backed.
; Vectors and Lists are java classes too!
(class [1 2 3]); => clojure.lang.PersistentVector
(class '(1 2 3)); => clojure.lang.PersistentList
@@ -76,16 +80,18 @@ and often automatically.
; it to stop the reader thinking it's a function.
; Also, (list 1 2 3) is the same as '(1 2 3)
+; "Collections" are just groups of data
; Both lists and vectors are collections:
(coll? '(1 2 3)) ; => true
(coll? [1 2 3]) ; => true
+; "Sequences" (seqs) are abstract descriptions of lists of data.
; Only lists are seqs.
(seq? '(1 2 3)) ; => true
(seq? [1 2 3]) ; => false
-; Seqs are an interface for logical lists, which can be lazy.
-; "Lazy" means that a seq can define an infinite series, like so:
+; A seq need only provide an entry when it is accessed.
+; So, seqs which can be lazy -- they can define infinite series:
(range 4) ; => (0 1 2 3)
(range) ; => (0 1 2 3 4 ...) (an infinite series)
(take 4 (range)) ; (0 1 2 3)
@@ -94,8 +100,8 @@ and often automatically.
(cons 4 [1 2 3]) ; => (4 1 2 3)
(cons 4 '(1 2 3)) ; => (4 1 2 3)
-; Use conj to add an item to the beginning of a list,
-; or the end of a vector
+; Conj will add an item to a collection in the most efficient way.
+; For lists, they insert at the beginning. For vectors, they insert at the end.
(conj [1 2 3] 4) ; => [1 2 3 4]
(conj '(1 2 3) 4) ; => (4 1 2 3)
@@ -165,20 +171,26 @@ x ; => 1
; => "Hello Finn, you passed 3 extra args"
-; Hashmaps
+; Maps
;;;;;;;;;;
+; Hash maps and array maps share an interface. Hash maps have faster lookups
+; but don't retain key order.
(class {:a 1 :b 2 :c 3}) ; => clojure.lang.PersistentArrayMap
+(class (hash-map :a 1 :b 2 :c 3)) ; => clojure.lang.PersistentHashMap
+
+; Arraymaps will automatically become hashmaps through most operations
+; if they get big enough, so you don't need to worry.
+; Maps can use any hashable type as a key, but usually keywords are best
; Keywords are like strings with some efficiency bonuses
(class :a) ; => clojure.lang.Keyword
-; Maps can use any type as a key, but usually keywords are best
-(def stringmap (hash-map "a" 1, "b" 2, "c" 3))
+(def stringmap {"a" 1, "b" 2, "c" 3})
stringmap ; => {"a" 1, "b" 2, "c" 3}
-(def keymap (hash-map :a 1 :b 2 :c 3))
-keymap ; => {:a 1, :c 3, :b 2} (order is not guaranteed)
+(def keymap {:a 1, :b 2, :c 3})
+keymap ; => {:a 1, :c 3, :b 2}
; By the way, commas are always treated as whitespace and do nothing.
@@ -197,7 +209,8 @@ keymap ; => {:a 1, :c 3, :b 2} (order is not guaranteed)
(stringmap "d") ; => nil
; Use assoc to add new keys to hash-maps
-(assoc keymap :d 4) ; => {:a 1, :b 2, :c 3, :d 4}
+(def newkeymap (assoc keymap :d 4))
+newkeymap ; => {:a 1, :b 2, :c 3, :d 4}
; But remember, clojure types are immutable!
keymap ; => {:a 1, :b 2, :c 3}
@@ -268,6 +281,7 @@ keymap ; => {:a 1, :b 2, :c 3}
(require 'clojure.string)
; Use / to call functions from a module
+; Here, the module is clojure.string and the function is blank?
(clojure.string/blank? "") ; => true
; You can give a module a shorter name on import
@@ -311,4 +325,56 @@ keymap ; => {:a 1, :b 2, :c 3}
(doto (Calendar/getInstance)
(.set 2000 1 1 0 0 0)
.getTime) ; => A Date. set to 2000-01-01 00:00:00
+
+; STM
+;;;;;;;;;;;;;;;;;
+
+; Software Transactional Memory is the mechanism clojure uses to handle
+; persistent state. There are a few constructs in clojure that use this.
+
+; An atom is the simplest. Pass it an initial value
+(def my-atom (atom {}))
+
+; Update an atom with swap!.
+; swap! takes a function and calls it with the current value of the atom
+; as the first argument, and any trailing arguments as the second
+(swap! my-atom assoc :a 1) ; Sets my-atom to the result of (assoc {} :a 1)
+(swap! my-atom assoc :b 2) ; Sets my-atom to the result of (assoc {:a 1} :b 2)
+
+ ; Use '@' to dereference the atom and get the value
+my-atom ;=> Atom<#...> (Returns the Atom object)
+@my-atom ; => {:a 1 :b 2}
+
+; Here's a simple counter using an atom
+(def counter (atom 0))
+(defn inc-counter []
+ (swap! counter inc))
+
+(inc-counter)
+(inc-counter)
+(inc-counter)
+(inc-counter)
+(inc-counter)
+
+@counter ; => 5
+
+; Other STM constructs are refs and agents.
+; Refs: http://clojure.org/refs
+; Agents: http://clojure.org/agents
```
+
+### Further Reading
+
+This is far from exhaustive, but hopefully it's enought o get you on your feet.
+
+Clojure.org has lots of articles:
+[http://clojure.org/](http://clojure.org/)
+
+Clojuredocs.org has documentation with examples for most core functions:
+[http://clojuredocs.org/quickref/Clojure%20Core](http://clojuredocs.org/quickref/Clojure%20Core)
+
+4Clojure is a great way to build your clojure/FP skills:
+[http://www.4clojure.com/](http://www.4clojure.com/)
+
+Clojure-doc.org (yeah, really) has a number of getting started articles:
+[http://clojure-doc.org/](http://clojure-doc.org/)
diff --git a/dart.html.markdown b/dart.html.markdown
index c503fb4a..34d1c6a8 100644
--- a/dart.html.markdown
+++ b/dart.html.markdown
@@ -1,7 +1,8 @@
---
language: dart
-author: Joao Pedrosa
-author_url: https://github.com/jpedrosa/
+filename: learndart.dart
+contributors:
+ - ["Joao Pedrosa", "https://github.com/jpedrosa/"]
---
Dart is a newcomer into the realm of programming languages.
diff --git a/elixir.html.markdown b/elixir.html.markdown
new file mode 100644
index 00000000..8ea499ff
--- /dev/null
+++ b/elixir.html.markdown
@@ -0,0 +1,398 @@
+---
+language: elixir
+contributors:
+ - ["Joao Marques", "http://github.com/mrshankly"]
+filename: learnelixir.ex
+---
+
+Elixir is a modern functional language built on top of the Erlang VM.
+It's fully compatible with Erlang, but features a more standard syntax
+and many more features.
+
+```ruby
+
+# Single line comments start with a hashtag.
+
+# There's no multi-line comment,
+# but you can stack multiple comments.
+
+# To use the elixir shell use the `iex` command.
+# Compile your modules with the `elixirc` command.
+
+# Both should be in your path if you installed elixir correctly.
+
+## ---------------------------
+## -- Basic types
+## ---------------------------
+
+# There are numbers
+3 # integer
+0x1F # integer
+3.0 # float
+
+# Atoms, that are literals, a constant with name. They start with `:`.
+:hello # atom
+
+# Tuples that are stored contiguously in memory.
+{1,2,3} # tuple
+
+# We can access a tuple element with the `elem` function:
+elem({1, 2, 3}, 0) #=> 1
+
+# Lists that are implemented as linked lists.
+[1,2,3] # list
+
+# We can access the head and tail of a list as follows:
+[head | tail] = [1,2,3]
+head #=> 1
+tail #=> [2,3]
+
+# In elixir, just like in Erlang, the `=` denotes pattern matching and
+# not an assignment.
+#
+# This means that the left-hand side (pattern) is matched against a
+# right-hand side.
+#
+# This is how the above example of accessing the head and tail of a list works.
+
+# A pattern match will error when the sides don't match, in this example
+# the tuples have different sizes.
+# {a, b, c} = {1, 2} #=> ** (MatchError) no match of right hand side value: {1,2}
+
+# There's also binaries
+<<1,2,3>> # binary
+
+# Strings and char lists
+"hello" # string
+'hello' # char list
+
+# Multi-line strings
+"""
+I'm a multi-line
+string.
+"""
+#=> "I'm a multi-line\nstring.\n"
+
+# Strings are all encoded in UTF-8:
+"héllò" #=> "héllò"
+
+# Strings are really just binaries, and char lists are just lists.
+<<?a, ?b, ?c>> #=> "abc"
+[?a, ?b, ?c] #=> 'abc'
+
+# `?a` in elixir returns the ASCII integer for the letter `a`
+?a #=> 97
+
+# To concatenate lists use `++`, for binaries use `<>`
+[1,2,3] ++ [4,5] #=> [1,2,3,4,5]
+'hello ' ++ 'world' #=> 'hello world'
+
+<<1,2,3>> <> <<4,5>> #=> <<1,2,3,4,5>>
+"hello " <> "world" #=> "hello world"
+
+## ---------------------------
+## -- Operators
+## ---------------------------
+
+# Some math
+1 + 1 #=> 2
+10 - 5 #=> 5
+5 * 2 #=> 10
+10 / 2 #=> 5.0
+
+# In elixir the operator `/` always returns a float.
+
+# To do integer division use `div`
+div(10, 2) #=> 5
+
+# To get the division remainder use `rem`
+rem(10, 3) #=> 1
+
+# There's also boolean operators: `or`, `and` and `not`.
+# These operators expect a boolean as their first argument.
+true and true #=> true
+false or true #=> true
+# 1 and true #=> ** (ArgumentError) argument error
+
+# Elixir also provides `||`, `&&` and `!` which accept arguments of any type.
+# All values except `false` and `nil` will evaluate to true.
+1 || true #=> 1
+false && 1 #=> false
+nil && 20 #=> nil
+
+!true #=> false
+
+# For comparisons we have: `==`, `!=`, `===`, `!==`, `<=`, `>=`, `<` and `>`
+1 == 1 #=> true
+1 != 1 #=> false
+1 < 2 #=> true
+
+# `===` and `!==` are more strict when comparing integers and floats:
+1 == 1.0 #=> true
+1 === 1.0 #=> false
+
+# We can also compare two different data types:
+1 < :hello #=> true
+
+# The overall sorting order is defined below:
+# number < atom < reference < functions < port < pid < tuple < list < bit string
+
+# To quote Joe Armstrong on this: "The actual order is not important,
+# but that a total ordering is well defined is important."
+
+## ---------------------------
+## -- Control Flow
+## ---------------------------
+
+# `if` expression
+if false do
+ "This will never be seen"
+else
+ "This will"
+end
+
+# There's also `unless`
+unless true do
+ "This will never be seen"
+else
+ "This will"
+end
+
+# Remember pattern matching? Many control-flow structures in elixir rely on it.
+
+# `case` allows us to compare a value against many patterns:
+case {:one, :two} do
+ {:four, :five} ->
+ "This won't match"
+ {:one, x} ->
+ "This will match and assign `x` to `:two`"
+ _ ->
+ "This will match any value"
+end
+
+# It's common practice to assign a value to `_` if we don't need it.
+# For example, if only the head of a list matters to us:
+[head | _] = [1,2,3]
+head #=> 1
+
+# For better readability we can do the following:
+[head | _tail] = [:a, :b, :c]
+head #=> :a
+
+# `cond` lets us check for many conditions at the same time.
+# Use `cond` instead of nesting many `if` expressions.
+cond do
+ 1 + 1 == 3 ->
+ "I will never be seen"
+ 2 * 5 == 12 ->
+ "Me neither"
+ 1 + 2 == 3 ->
+ "But I will"
+end
+
+# It is common to see a last condition equal to `true`, which will always match.
+cond do
+ 1 + 1 == 3 ->
+ "I will never be seen"
+ 2 * 5 == 12 ->
+ "Me neither"
+ true ->
+ "But I will (this is essentially an else)"
+end
+
+# `try/catch` is used to catch values that are thrown, it also supports an
+# `after` clause that is invoked whether or not a value is catched.
+try do
+ throw(:hello)
+catch
+ message -> "Got #{message}."
+after
+ IO.puts("I'm the after clause.")
+end
+#=> I'm the after clause
+# "Got :hello"
+
+## ---------------------------
+## -- Modules and Functions
+## ---------------------------
+
+# Anonymous functions (notice the dot)
+square = fn(x) -> x * x end
+square.(5) #=> 25
+
+# They also accept many clauses and guards.
+# Guards let you fine tune pattern matching,
+# they are indicated by the `when` keyword:
+f = fn
+ x, y when x > 0 -> x + y
+ x, y -> x * y
+end
+
+f.(1, 3) #=> 4
+f.(-1, 3) #=> -3
+
+# Elixir also provides many built-in functions.
+# These are available in the current scope.
+is_number(10) #=> true
+is_list("hello") #=> false
+elem({1,2,3}, 0) #=> 1
+
+# You can group several functions into a module. Inside a module use `def`
+# to define your functions.
+defmodule Math do
+ def sum(a, b) do
+ a + b
+ end
+
+ def square(x) do
+ x * x
+ end
+end
+
+Math.sum(1, 2) #=> 3
+Math.square(3) #=> 9
+
+# To compile our simple Math module save it as `math.ex` and use `elixirc`
+# in your terminal: elixirc math.ex
+
+# Inside a module we can define functions with `def` and private functions with `defp`.
+# A function defined with `def` is available to be invoked from other modules,
+# a private function can only be invoked locally.
+defmodule PrivateMath do
+ def sum(a, b) do
+ do_sum(a, b)
+ end
+
+ defp do_sum(a, b) do
+ a + b
+ end
+end
+
+PrivateMath.sum(1, 2) #=> 3
+# PrivateMath.do_sum(1, 2) #=> ** (UndefinedFunctionError)
+
+# Function declarations also support guards and multiple clauses:
+defmodule Geometry do
+ def area({:rectangle, w, h}) do
+ w * h
+ end
+
+ def area({:circle, r}) when is_number(r) do
+ 3.14 * r * r
+ end
+end
+
+Geometry.area({:rectangle, 2, 3}) #=> 6
+Geometry.area({:circle, 3}) #=> 28.25999999999999801048
+# Geometry.area({:circle, "not_a_number"})
+#=> ** (FunctionClauseError) no function clause matching in Geometry.area/1
+
+# Due to immutability, recursion is a big part of elixir
+defmodule Recursion do
+ def sum_list([head | tail], acc) do
+ sum_list(tail, acc + head)
+ end
+
+ def sum_list([], acc) do
+ acc
+ end
+end
+
+Recursion.sum_list([1,2,3], 0) #=> 6
+
+# Elixir modules support attributes, there are built-in attributes and you
+# may also add custom attributes.
+defmodule MyMod do
+ @moduledoc """
+ This is a built-in attribute on a example module.
+ """
+
+ @my_data 100 # This is a custom attribute.
+ IO.inspect(@my_data) #=> 100
+end
+
+## ---------------------------
+## -- Records and Exceptions
+## ---------------------------
+
+# Records are basically structures that allow you to associate a name with
+# a particular value.
+defrecord Person, name: nil, age: 0, height: 0
+
+joe_info = Person.new(name: "Joe", age: 30, height: 180)
+#=> Person[name: "Joe", age: 30, height: 180]
+
+# Access the value of name
+joe_info.name #=> "Joe"
+
+# Update the value of age
+joe_info = joe_info.age(31) #=> Person[name: "Joe", age: 31, height: 180]
+
+# The `try` block with the `rescue` keyword is used to handle exceptions
+try do
+ raise "some error"
+rescue
+ RuntimeError -> "rescued a runtime error"
+ _error -> "this will rescue any error"
+end
+
+# All exceptions have a message
+try do
+ raise "some error"
+rescue
+ x in [RuntimeError] ->
+ x.message
+end
+
+## ---------------------------
+## -- Concurrency
+## ---------------------------
+
+# Elixir relies on the actor model for concurrency. All we need to write
+# concurrent programs in elixir are three primitives: spawning processes,
+# sending messages and receiving messages.
+
+# To start a new process we use the `spawn` function, which takes a function
+# as argument.
+f = fn -> 2 * 2 end #=> #Function<erl_eval.20.80484245>
+spawn(f) #=> #PID<0.40.0>
+
+# `spawn` returns a pid (process identifier), you can use this pid to send
+# messages to the process. To do message passing we use the `<-` operator.
+# For all of this to be useful we need to be able to receive messages. This is
+# achived with the `receive` mechanism:
+defmodule Geometry do
+ def area_loop do
+ receive do
+ {:rectangle, w, h} ->
+ IO.puts("Area = #{w * h}")
+ area_loop()
+ {:circle, r} ->
+ IO.puts("Area = #{3.14 * r * r}")
+ area_loop()
+ end
+ end
+end
+
+# Compile the module and create a process that evaluates `area_loop` in the shell
+pid = spawn(fn -> Geometry.area_loop() end) #=> #PID<0.40.0>
+
+# Send a message to `pid` that will match a pattern in the receive statement
+pid <- {:rectangle, 2, 3}
+#=> Area = 6
+# {:rectangle,2,3}
+
+pid <- {:circle, 2}
+#=> Area = 12.56000000000000049738
+# {:circle,2}
+
+# The shell is also a process, you can use `self` to get the current pid
+self() #=> #PID<0.27.0>
+```
+
+## References
+
+* [Getting started guide](http://elixir-lang.org/getting_started/1.html) from [elixir webpage](http://elixir-lang.org)
+* [Elixir Documentation](http://elixir-lang.org/docs/master/)
+* ["Learn You Some Erlang for Great Good!"](http://learnyousomeerlang.com/) by Fred Hebert
+* "Programming Erlang: Software for a Concurrent World" by Joe Armstrong
diff --git a/erlang.html.markdown b/erlang.html.markdown
new file mode 100644
index 00000000..208f31e4
--- /dev/null
+++ b/erlang.html.markdown
@@ -0,0 +1,239 @@
+---
+language: erlang
+contributor:
+ - ["Giovanni Cappellotto", "http://www.focustheweb.com/"]
+filename: learnerlang.erl
+---
+
+```erlang
+% Percent sign start a one-line comment.
+
+%% Two percent characters shall be used to comment functions.
+
+%%% Three percent characters shall be used to comment modules.
+
+% We use three types of punctuation in Erlang.
+% Commas (`,`) separate arguments in function calls, data constructors, and
+% patterns.
+% Periods (`.`) (followed by whitespace) separate entire functions and
+% expressions in the shell.
+% Semicolons (`;`) separate clauses. We find clauses in several contexts: in kn
+% function definitions and in `case`, `if`, `try..catch` and `receive`
+% expressions.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% 1. Variables and pattern matching.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+Num = 42. % All variable names must start with an uppercase letter.
+% Erlang has single assignment variables, if you try to assign a different value
+% to the variable `Num`, you’ll get an error.
+
+% In most languages, `=` denotes an assignment statement. In Erlang, however,
+% `=` denotes a pattern matching operation. `Lhs = Rhs` really means this:
+% evaluate the right side (Rhs), and then match the result against the pattern
+% on the left side (Lhs).
+Num = 7 * 6.
+
+% Floating point number.
+Pi = 3.14159.
+
+% Atoms, are used to represent different non-numerical constant values. Atoms
+% start with lowercase letters, followed by a sequence of alphanumeric
+% characters or the underscore (`_`) or at (`@`) sign.
+Hello = hello.
+
+% Tuples are similar to structs in C.
+Point = {point, 10, 45}.
+
+% If we want to extract some values from a tuple, we use the pattern matching
+% operator `=`.
+{point, X, Y} = Point. % X = 10, Y = 45
+
+% We can use `_` as a placeholder for variables that we’re not interested in.
+% The symbol `_` is called an anonymous variable. Unlike regular variables,
+% several occurrences of _ in the same pattern don’t have to bind to the same
+% value.
+Person = {person, {name, {first, joe}, {last, armstrong}}, {footsize, 42}}.
+{_, {_, {_, Who}, _}, _} = Person. % Who = joe
+
+% We create a list by enclosing the list elements in square brackets and
+% separating them with commas.
+% The individual elements of a list can be of any type.
+% The first element of a list the head of the list. If you imagine removing the
+% head from the list, what’s left is called the tail of the list.
+ThingsToBuy = [{apples, 10}, {pears, 6}, {milk, 3}].
+
+% If `T` is a list, then `[H|T]` is also a list, with head H and tail T.
+% The vertical bar (`|`) separates the head of a list from its tail.
+% `[]` is the empty list.
+% We can extract elements from a list with a pattern matching operation. If we
+% have the nonempty list `L`, then the expression `[X|Y] = L`, where `X` and `Y`
+% are unbound variables, will extract the head of the list into `X` and the tail
+% of the list into `Y`.
+[FirstThing|OtherThingsToBuy] = ThingsToBuy.
+% FirstThing = {apples, 10}
+% OtherThingsToBuy = {pears, 6}, {milk, 3}
+
+% There are no strings in Erlang. Strings are really just lists of integers.
+% Strings are enclosed in double quotation marks (`"`).
+Name = "Hello".
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% 2. Sequential programming.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+% Modules are the basic unit of code in Erlang. All the functions we write are
+% stored in modules. Modules are stored in files with `.erl` extensions.
+% Modules must be compiled before the code can be run. A compiled module has the
+% extension `.beam`.
+-module(geometry).
+-export([area/1]).
+
+% The function area consists of two clauses. The clauses are separated by a
+% semicolon, and the final clause is terminated by dot-whitespace.
+% Each clause has a head and a body; the head consists of a function name
+% followed by a pattern (in parentheses), and the body consists of a sequence of
+% expressions, which are evaluated if the pattern in the head is successfully
+% matched against the calling arguments. The patterns are matched in the order
+% they appear in the function definition.
+area({rectangle, Width, Ht}) -> Width * Ht;
+area({circle, R}) -> 3.14159 * R * R.
+
+% Compile the code in the file geometry.erl.
+c(geometry). % {ok,geometry}
+
+% We need to include the module name together with the function name in order to
+% identify exactly which function we want to call.
+geometry:area({rectangle, 10, 5}). % 50
+geometry:area({circle, 1.4}). % 6.15752
+
+% In Erlang, two functions with the same name and different arity in the same
+% module represent entirely different functions.
+-module(lib_misc).
+-export([sum/1]).
+sum(L) -> sum(L, 0).
+sum([], N) -> N;
+sum([H|T], N) -> sum(T, H+N).
+
+% Funs are "anonymous" functions. They are called this because they have no
+% name.
+Double = fun(X) -> 2*X end.
+Double(2). % 4
+
+% Functions accept funs as their arguments and can return funs.
+Mult = fun(Times) -> ( fun(X) -> X * Times end ) end.
+Triple = Mult(3).
+Triple(5). % 15
+
+% List comprehensions are expressions that create lists without having to use
+% funs, maps, or filters.
+% The notation `[F(X) || X <- L]` means "the list of `F(X)` where `X` is taken
+% from the list `L`."
+L = [1,2,3,4,5].
+[2*X || X <- L]. % [2,4,6,8,10]
+
+% Guards are constructs that we can use to increase the power of pattern
+% matching. Using guards, we can perform simple tests and comparisons on the
+% variables in a pattern.
+% You can use guards in the heads of function definitions where they are
+% introduced by the `when` keyword, or you can use them at any place in the
+% language where an expression is allowed.
+max(X, Y) when X > Y -> X;
+max(X, Y) -> Y.
+
+% A guard is a series of guard expressions, separated by commas (`,`).
+% The guard `GuardExpr1, GuardExpr2, ..., GuardExprN` is true if all the guard
+% expressions `GuardExpr1, GuardExpr2, ...` evaluate to true.
+is_cat(A) when is_atom(A), A =:= cat -> true;
+is_cat(A) -> false.
+is_dog(A) when is_atom(A), A =:= dog -> true;
+is_dog(A) -> false.
+
+% A `guard sequence` is either a single guard or a series of guards, separated
+%by semicolons (`;`). The guard sequence `G1; G2; ...; Gn` is true if at least
+% one of the guards `G1, G2, ...` evaluates to true.
+is_pet(A) when is_dog(A); is_cat(A) -> true;
+is_pet(A) -> false.
+
+% Records provide a method for associating a name with a particular element in a
+% tuple.
+% Record definitions can be included in Erlang source code files or put in files
+% with the extension `.hrl`, which are then included by Erlang source code
+% files.
+-record(todo, {
+ status = reminder, % Default value
+ who = joe,
+ text
+}).
+
+% We have to read the record definitions into the shell before we can define a
+% record. We use the shell function `rr` (short for read records) to do this.
+rr("records.hrl"). % [todo]
+
+% Creating and updating records:
+X = #todo{}.
+% #todo{status = reminder, who = joe, text = undefined}
+X1 = #todo{status = urgent, text = "Fix errata in book"}.
+% #todo{status = urgent, who = joe, text = "Fix errata in book"}
+X2 = X1#todo{status = done}.
+% #todo{status = done,who = joe,text = "Fix errata in book"}
+
+% `case` expressions.
+% `filter` returns a list of all those elements `X` in `L` for which `P(X)` is
+% true.
+filter(P, [H|T]) ->
+ case P(H) of
+ true -> [H|filter(P, T)];
+ false -> filter(P, T)
+ end;
+filter(P, []) -> [].
+
+% `if` expressions.
+max(X, Y) ->
+ if
+ X > Y -> X;
+ X < Y -> Y;
+ true -> nil;
+ end.
+
+% Warning: at least one of the guards in the if expression must evaluate to true;
+% otherwise, an exception will be raised.
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%% 3. Exceptions.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+% Exceptions are raised by the system when internal errors are encountered or
+% explicitly in code by calling `throw(Exception)`, `exit(Exception)` or
+% `erlang:error(Exception)`.
+generate_exception(1) -> a;
+generate_exception(2) -> throw(a);
+generate_exception(3) -> exit(a);
+generate_exception(4) -> {'EXIT', a};
+generate_exception(5) -> erlang:error(a).
+
+% Erlang has two methods of catching an exception. One is to enclose the call to
+% the function, which raised the exception within a `try...catch` expression.
+catcher(N) ->
+ try generate_exception(N) of
+ Val -> {N, normal, Val}
+ catch
+ throw:X -> {N, caught, thrown, X};
+ exit:X -> {N, caught, exited, X};
+ error:X -> {N, caught, error, X}
+ end.
+
+% The other is to enclose the call in a `catch` expression. When you catch an
+% exception, it is converted into a tuple that describes the error.
+catcher(N) -> catch generate_exception(N).
+
+```
+
+## References
+
+* "Programming Erlang: Software for a Concurrent World" by Joe Armstrong
+* [Erlang - Programming Rules and Conventions](http://www.erlang.se/doc/programming_rules.shtml)
+* [Erlang/OTP Documentation](http://www.erlang.org/doc/)
diff --git a/file.erb b/file.erb
new file mode 100644
index 00000000..5f162aa5
--- /dev/null
+++ b/file.erb
@@ -0,0 +1 @@
+<%= rawcode %>
diff --git a/fsharp.html.markdown b/fsharp.html.markdown
index 1deaf437..49951c78 100644
--- a/fsharp.html.markdown
+++ b/fsharp.html.markdown
@@ -1,7 +1,8 @@
---
language: F#
-author: Scott Wlaschin
-author_url: http://fsharpforfunandprofit.com/
+contributors:
+ - ["Scott Wlaschin", "http://fsharpforfunandprofit.com/"]
+filename: learnfsharp.fs
---
F# is a general purpose functional/OO programming language. It's free and open source, and runs on Linux, Mac, Windows and more.
diff --git a/haskell.html.markdown b/haskell.html.markdown
index 563674c9..be7d8669 100644
--- a/haskell.html.markdown
+++ b/haskell.html.markdown
@@ -1,17 +1,17 @@
---
language: haskell
-author: Adit Bhargava
-author_url: http://adit.io
+contributors:
+ - ["Adit Bhargava", "http://adit.io"]
---
Haskell was designed as a practical, purely functional programming language. It's famous for
-it's monads and it's type system, but I keep coming back to it because of it's elegance. Haskell
+its monads and its type system, but I keep coming back to it because of its elegance. Haskell
makes coding a real joy for me.
```haskell
-- Single line comments start with two dashes.
{- Multiline comments can be enclosed
-in a block like this.
+en a block like this.
-}
----------------------------------------------------
@@ -44,15 +44,21 @@ not False -- True
1 /= 1 -- False
1 < 10 -- True
+-- In the above examples, `not` is a function that takes one value.
+-- Haskell doesn't need parentheses for function calls...all the arguments
+-- are just listed after the function. So the general pattern is:
+-- func arg1 arg2 arg3...
+-- See the section on functions for information on how to write your own.
+
-- Strings and characters
"This is a string."
'a' -- character
'You cant use single quotes for strings.' -- error!
--- Strings can be added too!
+-- Strings can be concatenated
"Hello " ++ "world!" -- "Hello world!"
--- A string can be treated like a list of characters
+-- A string is a list of characters
"This is a string" !! 0 -- 'T'
@@ -68,14 +74,24 @@ not False -- True
-- You can also have infinite lists in Haskell!
[1..] -- a list of all the natural numbers
--- joining two lists
+-- Infinite lists work because Haskell has "lazy evaluation". This means
+-- that Haskell only evaluates things when it needs to. So you can ask for
+-- the 1000th element of your list and Haskell will give it to you:
+
+[1..] !! 999 -- 1000
+
+-- And now Haskell has evaluated elements 1 - 1000 of this list...but the
+-- rest of the elements of this "infinite" list don't exist yet! Haskell won't
+-- actually evaluate them until it needs to.
+
+- joining two lists
[1..5] ++ [6..10]
-- adding to the head of a list
0:[1..5] -- [0, 1, 2, 3, 4, 5]
-- indexing into a list
-[0..] !! 5 -- 4
+[0..] !! 5 -- 5
-- more list operations
head [1..5] -- 1
@@ -104,6 +120,10 @@ snd ("haskell", 1) -- 1
-- A simple function that takes two variables
add a b = a + b
+-- Note that if you are using ghci (the Haskell interpreter)
+-- You'll need to use `let`, i.e.
+-- let add a b = a + b
+
-- Using the function
add 1 2 -- 3
@@ -132,19 +152,19 @@ fib x = fib (x - 1) + fib (x - 2)
-- Pattern matching on tuples:
foo (x, y) = (x + 1, y + 2)
--- Pattern matching on arrays. Here `x` is the first element
--- in the array, and `xs` is the rest of the array. We can write
+-- Pattern matching on lists. Here `x` is the first element
+-- in the list, and `xs` is the rest of the list. We can write
-- our own map function:
-map func [x] = [func x]
-map func (x:xs) = func x:(map func xs)
+myMap func [] = []
+myMap func (x:xs) = func x:(myMap func xs)
-- Anonymous functions are created with a backslash followed by
-- all the arguments.
-map (\x -> x + 2) [1..5] -- [3, 4, 5, 6, 7]
+myMap (\x -> x + 2) [1..5] -- [3, 4, 5, 6, 7]
-- using fold (called `inject` in some languages) with an anonymous
-- function. foldl1 means fold left, and use the first value in the
--- array as the initial value for the accumulator.
+-- list as the initial value for the accumulator.
foldl1 (\acc x -> acc + x) [1..5] -- 15
----------------------------------------------------
@@ -179,10 +199,10 @@ foo 5 -- 75
-- of parentheses:
-- before
-(even (double 7)) -- true
+(even (fib 7)) -- true
-- after
-even . double $ 7 -- true
+even . fib $ 7 -- true
----------------------------------------------------
-- 5. Type signatures
@@ -197,13 +217,17 @@ True :: Bool
-- Functions have types too.
-- `not` takes a boolean and returns a boolean:
-not :: Bool -> Bool
+-- not :: Bool -> Bool
-- Here's a function that takes two arguments:
-add :: Integer -> Integer -> Integer
+-- add :: Integer -> Integer -> Integer
+
+-- When you define a value, it's good practice to write its type above it:
+double :: Integer -> Integer
+double x = x * 2
----------------------------------------------------
--- 6. Control Flow
+-- 6. Control Flow and If Statements
----------------------------------------------------
-- if statements
@@ -221,7 +245,7 @@ case args of
_ -> putStrLn "bad args"
-- Haskell doesn't have loops because it uses recursion instead.
--- map a function over every element in an array
+-- map applies a function over every element in an array
map (*2) [1..5] -- [2, 4, 6, 8, 10]
@@ -234,6 +258,19 @@ for [0..5] $ \i -> show i
-- we could've written that like this too:
for [0..5] show
+-- You can use foldl or foldr to reduce a list
+-- foldl <fn> <initial value> <list>
+foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43
+
+-- This is the same as
+(2 * (2 * (2 * 4 + 1) + 2) + 3)
+
+-- foldl is left-handed, foldr is right-
+foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16
+
+-- This is now the same as
+(2 * 3 + (2 * 2 + (2 * 1 + 4)))
+
----------------------------------------------------
-- 7. Data Types
----------------------------------------------------
@@ -244,22 +281,104 @@ data Color = Red | Blue | Green
-- Now you can use it in a function:
-say :: Color -> IO String
-say Red = putStrLn "You are Red!"
-say Blue = putStrLn "You are Blue!"
-say Green = putStrLn "You are Green!"
+
+say :: Color -> String
+say Red = "You are Red!"
+say Blue = "You are Blue!"
+say Green = "You are Green!"
-- Your data types can have parameters too:
data Maybe a = Nothing | Just a
-- These are all of type Maybe
-Nothing
-Just "hello"
-Just 1
+Just "hello" -- of type `Maybe String`
+Just 1 -- of type `Maybe Int`
+Nothing -- of type `Maybe a` for any `a`
+
+----------------------------------------------------
+-- 8. Haskell IO
+----------------------------------------------------
+
+-- While IO can't be explained fully without explaining monads,
+-- it is not hard to explain enough to get going.
+
+-- When a Haskell program is executed, the function `main` is
+-- called. It must return a value of type `IO ()`. For example:
+
+main :: IO ()
+main = putStrLn $ "Hello, sky! " ++ (say Blue)
+-- putStrLn has type String -> IO ()
+
+-- It is easiest to do IO if you can implement your program as
+-- a function from String to String. The function
+-- interact :: (String -> String) -> IO ()
+-- inputs some text, runs a function on it, and prints out the
+-- output.
+
+countLines :: String -> String
+countLines = show . length . lines
+
+main' = interact countLines
+
+-- You can think of a value of type `IO ()` as representing a
+-- sequence of actions for the computer to do, much like a
+-- computer program written in an imperative language. We can use
+-- the `do` notation to chain actions together. For example:
+
+sayHello :: IO ()
+sayHello = do
+ putStrLn "What is your name?"
+ name <- getLine -- this gets a line and gives it the name "input"
+ putStrLn $ "Hello, " ++ name
+
+-- Exercise: write your own version of `interact` that only reads
+-- one line of input.
+
+-- The code in `sayHello` will never be executed, however. The only
+-- action that ever gets executed is the value of `main`.
+-- To run `sayHello` comment out the above definition of `main`
+-- and replace it with:
+-- main = sayHello
+
+-- Let's understand better how the function `getLine` we just
+-- used works. Its type is:
+-- getLine :: IO String
+-- You can think of a value of type `IO a` as representing a
+-- computer program that will generate a value of type `a`
+-- when executed (in addition to anything else it does). We can
+-- store and reuse this value using `<-`. We can also
+-- make our own action of type `IO String`:
+
+action :: IO String
+action = do
+ putStrLn "This is a line. Duh"
+ input1 <- getLine
+ input2 <- getLine
+ -- The type of the `do` statement is that of its last line.
+ -- `return` is not a keyword, but merely a function
+ return (input1 ++ "\n" ++ input2) -- return :: String -> IO String
+
+-- We can use this just like we used `getLine`:
+
+main'' = do
+ putStrLn "I will echo two lines!"
+ result <- action
+ putStrLn result
+ putStrLn "This was all, folks!"
+
+-- The type `IO` is an example of a "monad". The way Haskell uses a monad to
+-- do IO allows it to be a purely functional language. Any function that
+-- interacts with the outside world (i.e. does IO) gets marked as `IO` in its
+-- type signature. This lets us reason about what functions are "pure" (don't
+-- interact with the outside world or modify state) and what functions aren't.
+
+-- This is a powerful feature, because it's easy to run pure functions
+-- concurrently; so, concurrency in Haskell is very easy.
+
----------------------------------------------------
--- 8. The Haskell REPL
+-- 9. The Haskell REPL
----------------------------------------------------
-- Start the repl by typing `ghci`.
@@ -272,6 +391,14 @@ let foo = 5
>:t foo
foo :: Integer
+
+-- You can also run any action of type `IO ()`
+
+> sayHello
+What is your name?
+Friend!
+Hello, Friend!
+
```
There's a lot more to Haskell, including typeclasses and monads. These are the big ideas that make Haskell such fun to code in. I'll leave you with one final Haskell example: an implementation of quicksort in Haskell:
@@ -285,5 +412,6 @@ qsort (p:xs) = qsort lesser ++ [p] ++ qsort greater
Haskell is easy to install. Get it [here](http://www.haskell.org/platform/).
-You can find a much gentler introduction from the excellent [Learn you a Haskell](http://learnyouahaskell.com/)
-
+You can find a much gentler introduction from the excellent
+[Learn you a Haskell](http://learnyouahaskell.com/) or
+[Real World Haskell](http://book.realworldhaskell.org/).
diff --git a/java.html.markdown b/java.html.markdown
new file mode 100644
index 00000000..a6026651
--- /dev/null
+++ b/java.html.markdown
@@ -0,0 +1,407 @@
+---
+
+language: java
+contributors:
+ - ["Jake Prather", "http://github.com/JakeHP"]
+filename: LearnJava.java
+
+---
+
+Java is a general-purpose, concurrent, class-based, object-oriented computer programming language.
+[Read more here.](http://docs.oracle.com/javase/tutorial/java/index.html)
+
+```java
+// Single-line comments start with //
+/*
+Multi-line comments look like this.
+*/
+/**
+JavaDoc comments look like this. Used to describe the Class or various
+attributes of a Class.
+*/
+
+// Import ArrayList class inside of the java.util package
+import java.util.ArrayList;
+// Import all classes inside of java.security package
+import java.security.*;
+
+// Each .java file contains one public class, with the same name as the file.
+public class LearnJava {
+
+ // A program must have a main method as an entry point
+ public static void main (String[] args) {
+
+ // Use System.out.println to print lines
+ System.out.println("Hello World!");
+ System.out.println(
+ "Integer: " + 10 +
+ " Double: " + 3.14 +
+ " Boolean: " + true);
+
+ // To print without a newline, use System.out.print
+ System.out.print("Hello ");
+ System.out.print("World");
+
+
+ ///////////////////////////////////////
+ // Types & Variables
+ ///////////////////////////////////////
+
+ // Declare a variable using <type> <name> [
+ // Byte - 8-bit signed two's complement integer
+ // (-128 <= byte <= 127)
+ byte fooByte = 100;
+
+ // Short - 16-bit signed two's complement integer
+ // (-32,768 <= short <= 32,767)
+ short fooShort = 10000;
+
+ // Integer - 32-bit signed two's complement integer
+ // (-2,147,483,648 <= int <= 2,147,483,647)
+ int fooInt = 1;
+
+ // Long - 64-bit signed two's complement integer
+ // (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
+ long fooLong = 100000L;
+ // L is used to denote that this variable value is of type Long;
+ // anything without is treated as integer by default.
+
+ // Note: Java has no unsigned types
+
+ // Float - Single-precision 32-bit IEEE 754 Floating Point
+ float fooFloat = 234.5f;
+ // f is used to denote that this variable value is of type float;
+ // otherwise it is treated as double.
+
+ // Double - Double-precision 64-bit IEEE 754 Floating Point
+ double fooDouble = 123.4;
+
+ // Boolean - true & false
+ boolean fooBoolean = true;
+ boolean barBoolean = false;
+
+ // Char - A single 16-bit Unicode character
+ char fooChar = 'A';
+
+ // Use final to make a variable immutable
+ final int HOURS_I_WORK_PER_WEEK = 9001;
+
+ // Strings
+ String fooString = "My String Is Here!";
+
+ // \n is an escaped character that starts a new line
+ String barString = "Printing on a new line?\nNo Problem!";
+ // \t is an escaped character that adds a tab character
+ String bazString = "Do you want to add a tab?\tNo Problem!";
+ System.out.println(fooString);
+ System.out.println(barString);
+ System.out.println(bazString);
+
+ // Arrays
+ //The array size must be decided upon declaration
+ //The format for declaring an array is follows:
+ //<datatype> [] <var name> = new <datatype>[<array size>];
+ int [] intArray = new int[10];
+ String [] stringArray = new String[1];
+ boolean [] booleanArray = new boolean[100];
+
+ // Another way to declare & initialize an array
+ int [] y = {9000, 1000, 1337};
+
+ // Indexing an array - Accessing an element
+ System.out.println("intArray @ 0: " + intArray[0]);
+
+ // Arrays are zero-indexed and mutable.
+ intArray[1] = 1;
+ System.out.println("intArray @ 1: " + intArray[1]); // => 1
+
+ // Others to check out
+ // ArrayLists - Like arrays except more functionality is offered,
+ // and the size is mutable
+ // LinkedLists
+ // Maps
+ // HashMaps
+
+ ///////////////////////////////////////
+ // Operators
+ ///////////////////////////////////////
+ System.out.println("\n->Operators");
+
+ int i1 = 1, i2 = 2; // Shorthand for multiple declarations
+
+ // Arithmetic is straightforward
+ System.out.println("1+2 = " + (i1 + i2)); // => 3
+ System.out.println("2-1 = " + (i2 - i1)); // => 1
+ System.out.println("2*1 = " + (i2 * i1)); // => 2
+ System.out.println("1/2 = " + (i1 / i2)); // => 0 (0.5 truncated down)
+
+ // Modulo
+ System.out.println("11%3 = "+(11 % 3)); // => 2
+
+ // Comparison operators
+ System.out.println("3 == 2? " + (3 == 2)); // => false
+ System.out.println("3 != 2? " + (3 != 2)); // => true
+ System.out.println("3 > 2? " + (3 > 2)); // => true
+ System.out.println("3 < 2? " + (3 < 2)); // => false
+ System.out.println("2 <= 2? " + (2 <= 2)); // => true
+ System.out.println("2 >= 2? " + (2 >= 2)); // => true
+
+ // Bitwise operators!
+ /*
+ ~ Unary bitwise complement
+ << Signed left shift
+ >> Signed right shift
+ >>> Unsigned right shift
+ & Bitwise AND
+ ^ Bitwise exclusive OR
+ | Bitwise inclusive OR
+ */
+
+ // Incrementations
+ int i = 0;
+ System.out.println("\n->Inc/Dec-rementation");
+ System.out.println(i++); //i = 1. Post-Incrementation
+ System.out.println(++i); //i = 2. Pre-Incrementation
+ System.out.println(i--); //i = 1. Post-Decrementation
+ System.out.println(--i); //i = 0. Pre-Decrementation
+
+ ///////////////////////////////////////
+ // Control Structures
+ ///////////////////////////////////////
+ System.out.println("\n->Control Structures");
+
+ // If statements are c-like
+ int j = 10;
+ if (j == 10){
+ System.out.println("I get printed");
+ } else if (j > 10) {
+ System.out.println("I don't");
+ } else {
+ System.out.println("I also don't");
+ }
+
+ // While loop
+ int fooWhile = 0;
+ while(fooWhile < 100)
+ {
+ //System.out.println(fooWhile);
+ //Increment the counter
+ //Iterated 99 times, fooWhile 0->99
+ fooWhile++;
+ }
+ System.out.println("fooWhile Value: " + fooWhile);
+
+ // Do While Loop
+ int fooDoWhile = 0;
+ do
+ {
+ //System.out.println(fooDoWhile);
+ //Increment the counter
+ //Iterated 99 times, fooDoWhile 0->99
+ fooDoWhile++;
+ }while(fooDoWhile < 100);
+ System.out.println("fooDoWhile Value: " + fooDoWhile);
+
+ // For Loop
+ int fooFor;
+ //for loop structure => for(<start_statement>; <conditional>; <step>)
+ for(fooFor=0; fooFor<10; fooFor++){
+ //System.out.println(fooFor);
+ //Iterated 10 times, fooFor 0->9
+ }
+ System.out.println("fooFor Value: " + fooFor);
+
+ // Switch Case
+ // A switch works with the byte, short, char, and int data types.
+ // It also works with enumerated types (discussed in Enum Types),
+ // the String class, and a few special classes that wrap
+ // primitive types: Character, Byte, Short, and Integer.
+ int month = 3;
+ String monthString;
+ switch (month){
+ case 1:
+ monthString = "January";
+ break;
+ case 2:
+ monthString = "February";
+ break;
+ case 3:
+ monthString = "March";
+ break;
+ default:
+ monthString = "Some other month";
+ break;
+ }
+ System.out.println("Switch Case Result: " + monthString);
+
+
+ ///////////////////////////////////////
+ // Converting Data Types And Typcasting
+ ///////////////////////////////////////
+
+ // Converting data
+
+ // Convert String To Integer
+ Integer.parseInt("123");//returns an integer version of "123"
+
+ // Convert Integer To String
+ Integer.toString(123);//returns a string version of 123
+
+ // For other conversions check out the following classes:
+ // Double
+ // Long
+ // String
+
+ // Typecasting
+ // You can also cast java objects, there's a lot of details and
+ // deals with some more intermediate concepts.
+ // Feel free to check it out here:
+ // http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html
+
+
+ ///////////////////////////////////////
+ // Classes And Functions
+ ///////////////////////////////////////
+
+ System.out.println("\n->Classes & Functions");
+
+ // (definition of the Bicycle class follows)
+
+ // Use new to instantiate a class
+ Bicycle trek = new Bicycle();
+
+ // Call object methods
+ trek.speedUp(3); // You should always use setter and getter methods
+ trek.setCadence(100);
+
+ // toString is a convention to display the value of this Object.
+ System.out.println("trek info: " + trek.toString());
+
+ } // End main method
+} // End LearnJava class
+
+
+// You can include other, non-public classes in a .java file
+
+
+// Class Declaration Syntax:
+// <public/private/protected> class <class name>{
+// //data fields, constructors, functions all inside.
+// //functions are called as methods in Java.
+// }
+
+class Bicycle {
+
+ // Bicycle's Fields/Variables
+ public int cadence; // Public: Can be accessed from anywhere
+ private int speed; // Private: Only accessible from within the class
+ protected int gear; // Protected: Accessible from the class and subclasses
+ String name; // default: Only accessible from within this package
+
+ // Constructors are a way of creating classes
+ // This is a default constructor
+ public Bicycle() {
+ gear = 1;
+ cadence = 50;
+ speed = 5;
+ name = "Bontrager";
+ }
+
+ // This is a specified constructor (it contains arguments)
+ public Bicycle(int startCadence, int startSpeed, int startGear, String name) {
+ this.gear = startGear;
+ this.cadence = startCadence;
+ this.speed = startSpeed;
+ this.name = name;
+ }
+
+ // Function Syntax:
+ // <public/private/protected> <return type> <function name>(<args>)
+
+ // Java classes often implement getters and setters for their fields
+
+ // Method declaration syntax:
+ // <scope> <return type> <method name>(<args>)
+ public int getCadence() {
+ return cadence;
+ }
+
+ // void methods require no return statement
+ public void setCadence(int newValue) {
+ cadence = newValue;
+ }
+
+ public void setGear(int newValue) {
+ gear = newValue;
+ }
+
+ public void speedUp(int increment) {
+ speed += increment;
+ }
+
+ public void slowDown(int decrement) {
+ speed -= decrement;
+ }
+
+ public void setName(int newName) {
+ name = newName;
+ }
+
+ public String getName() {
+ return name;
+ }
+
+ //Method to display the attribute values of this Object.
+ @Override
+ public String toString() {
+ return "gear: " + gear +
+ " cadence: " + cadence +
+ " speed: " + speed +
+ " name: " + name;
+ }
+} // end class Bicycle
+
+// PennyFarthing is a subclass of Bicycle
+class PennyFarthing extends Bicycle {
+ // (Penny Farthings are those bicycles with the big front wheel.
+ // They have no gears.)
+
+ public PennyFarthing(int startCadence, int startSpeed){
+ // Call the parent constructor with super
+ super(startCadence, startSpeed, 0, "PennyFarthing");
+ }
+
+ // You should mark a method you're overriding with an @annotation
+ // To learn more about what annotations are and their purpose
+ // check this out: http://docs.oracle.com/javase/tutorial/java/annotations/
+ @Override
+ public void setGear(int gear) {
+ gear = 0;
+ }
+
+}
+
+```
+
+## Further Reading
+
+The links provided here below are just to get an understanding of the topic, feel free to Google and find specific examples.
+
+Other Topics To Research:
+
+* [Java Tutorial Trail from Sun / Oracle](http://docs.oracle.com/javase/tutorial/index.html)
+
+* [Java Access level modifiers](http://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html)
+
+* [Object-Oriented Programming Concepts](http://docs.oracle.com/javase/tutorial/java/concepts/index.html):
+ * [Inheritance](http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html)
+ * [Polymorphism](http://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html)
+ * [Abstraction](http://docs.oracle.com/javase/tutorial/java/IandI/abstract.html)
+
+* [Exceptions](http://docs.oracle.com/javase/tutorial/essential/exceptions/index.html)
+
+* [Interfaces](http://docs.oracle.com/javase/tutorial/java/IandI/createinterface.html)
+
+* [Generics](http://docs.oracle.com/javase/tutorial/java/generics/index.html)
+
+* [Java Code Conventions](http://www.oracle.com/technetwork/java/codeconv-138413.html)
diff --git a/javascript.html.markdown b/javascript.html.markdown
new file mode 100644
index 00000000..cbe82054
--- /dev/null
+++ b/javascript.html.markdown
@@ -0,0 +1,433 @@
+---
+language: javascript
+author: Adam Brenecki
+author_url: http://adam.brenecki.id.au
+---
+
+Javascript was created by Netscape's Brendan Eich in 1995. It was originally
+intended as a simpler scripting language for websites, complimenting the use of
+Java for more complex web applications, but its tight integration with Web pages
+and built-in support in browsers has caused it to become far more common than
+Java in web frontends.
+
+JavaScript isn't just limited to web browsers, though: Node.js, a project that
+provides a standalone runtime for Google Chrome's V8 JavaScript engine, is
+becoming more and more popular.
+
+Feedback would be highly appreciated! You can reach me at
+[@adambrenecki](https://twitter.com/adambrenecki), or
+[adam@brenecki.id.au](mailto:adam@brenecki.id.au).
+
+```js
+// Comments are like C. Single-line comments start with two slashes,
+/* and multiline comments start with slash-star
+ and end with star-slash */
+
+// Statements can be terminated by ;
+doStuff();
+
+// ... but they don't have to be, as semicolons are automatically inserted
+// wherever there's a newline, except in certain cases.
+doStuff()
+
+// We'll leave semicolons off here; whether you do or not will depend on your
+// personal preference or your project's style guide.
+
+///////////////////////////////////
+// 1. Numbers, Strings and Operators
+
+// Javascript has one number type (which is a 64-bit IEEE 754 double).
+3 // = 3
+1.5 // = 1.5
+
+// All the basic arithmetic works as you'd expect.
+1 + 1 // = 2
+8 - 1 // = 7
+10 * 2 // = 20
+35 / 5 // = 7
+
+// Including uneven division.
+5 / 2 // = 2.5
+
+// Bitwise operations also work; when you perform a bitwise operation your float
+// is converted to a signed int *up to* 32 bits.
+1 << 2 // = 4
+
+// Precedence is enforced with parentheses.
+(1 + 3) * 2 // = 8
+
+// There are three special not-a-real-number values:
+Infinity // result of e.g. 1/0
+-Infinity // result of e.g. -1/0
+NaN // result of e.g. 0/0
+
+// There's also a boolean type.
+true
+false
+
+// Strings are created with ' or ".
+'abc'
+"Hello, world"
+
+// Negation uses the ! symbol
+!true // = false
+!false // = true
+
+// Equality is ==
+1 == 1 // = true
+2 == 1 // = false
+
+// Inequality is !=
+1 != 1 // = false
+2 != 1 // = true
+
+// More comparisons
+1 < 10 // = true
+1 > 10 // = false
+2 <= 2 // = true
+2 >= 2 // = true
+
+// Strings are concatenated with +
+"Hello " + "world!" // = "Hello world!"
+
+// and are compared with < and >
+"a" < "b" // = true
+
+// Type coercion is performed for comparisons...
+"5" == 5 // = true
+
+// ...unless you use ===
+"5" === 5 // = false
+
+// You can access characters in a string with charAt
+"This is a string".charAt(0)
+
+// There's also null and undefined
+null // used to indicate a deliberate non-value
+undefined // used to indicate a value that hasn't been set yet
+
+// null, undefined, NaN, 0 and "" are falsy, and everything else is truthy.
+// Note that 0 is falsy and "0" is truthy, even though 0 == "0".
+
+///////////////////////////////////
+// 2. Variables, Arrays and Objects
+
+// Variables are declared with the var keyword. Javascript is dynamically typed,
+// so you don't need to specify type. Assignment uses a single = character.
+var someVar = 5
+
+// if you leave the var keyword off, you won't get an error...
+someOtherVar = 10
+
+// ...but your variable will be created in the global scope, not in the scope
+// you defined it in.
+
+// Variables declared without being assigned to are set to undefined.
+var someThirdVar // = undefined
+
+// There's shorthand for performing math operations on variables:
+someVar += 5 // equivalent to someVar = someVar + 5; someVar is 10 now
+someVar *= 10 // now someVar is 100
+
+// and an even-shorter-hand for adding or subtracting 1
+someVar++ // now someVar is 101
+someVar-- // back to 100
+
+// Arrays are ordered lists of values, of any type.
+var myArray = ["Hello", 45, true]
+
+// Their members can be accessed using the square-brackets subscript syntax.
+// Array indices start at zero.
+myArray[1] // = 45
+
+// JavaScript's objects are equivalent to 'dictionaries' or 'maps' in other
+// languages: an unordered collection of key-value pairs.
+{key1: "Hello", key2: "World"}
+
+// Keys are strings, but quotes aren't required if they're a valid
+// JavaScript identifier. Values can be any type.
+var myObj = {myKey: "myValue", "my other key": 4}
+
+// Object attributes can also be accessed using the subscript syntax,
+myObj["my other key"] // = 4
+
+// ... or using the dot syntax, provided the key is a valid identifier.
+myObj.myKey // = "myValue"
+
+// Objects are mutable; values can be changed and new keys added.
+myObj.myThirdKey = true
+
+// If you try to access a value that's not yet set, you'll get undefined.
+myObj.myFourthKey // = undefined
+
+///////////////////////////////////
+// 3. Logic and Control Structures
+
+// The if structure works as you'd expect.
+var count = 1
+if (count == 3){
+ // evaluated if count is 3
+} else if (count == 4) {
+ // evaluated if count is 4
+} else {
+ // evaluated if it's not either 3 or 4
+}
+
+// As does while.
+while (true) {
+ // An infinite loop!
+}
+
+// Do-while loops are like while loops, except they always run at least once.
+var input
+do {
+ input = getInput()
+} while (!isValid(input))
+
+// the for loop is the same as C and Java:
+// initialisation; continue condition; iteration.
+for (var i = 0; i < 5; i++){
+ // will run 5 times
+}
+
+// && is logical and, || is logical or
+if (house.size == "big" && house.colour == "blue"){
+ house.contains = "bear"
+}
+if (colour == "red" || colour == "blue"){
+ // colour is either red or blue
+}
+
+// && and || "short circuit", which is useful for setting default values.
+var name = otherName || "default"
+
+///////////////////////////////////
+// 4. Functions, Scope and Closures
+
+// JavaScript functions are declared with the function keyword.
+function myFunction(thing){
+ return thing.toUpperCase()
+}
+myFunction("foo") // = "FOO"
+
+// Functions can also be defined "anonymously" - without a name:
+function(thing){
+ return thing.toLowerCase()
+}
+// (we can't call our function, since we don't have a name to refer to it with)
+
+// JavaScript functions are first class objects, so they can be reassigned to
+// different variable names and passed to other functions as arguments - for
+// example, when supplying an event handler:
+function myFunction(){
+ // this code will be called in 5 seconds' time
+}
+setTimeout(myFunction, 5000)
+
+// You can even write the function statement directly in the call to the other
+// function.
+
+setTimeout(function myFunction(){
+ // this code will be called in 5 seconds' time
+}, 5000)
+
+// JavaScript has function scope; functions get their own scope but other blocks
+// do not.
+if (true){
+ var i = 5
+}
+i // = 5 - not undefined as you'd expect in a block-scoped language
+
+// This has led to a common pattern of "immediately-executing anonymous
+// functions", which prevent temporary variables from leaking into the global
+// scope.
+function(){
+ var temporary = 5
+ // We can access the global scope by assiging to the 'global object', which
+ // in a web browser is always 'window'. The global object may have a
+ // different name in non-browser environments such as Node.js.
+ window.permanent = 10
+ // Or, as previously mentioned, we can just leave the var keyword off.
+ permanent2 = 15
+}()
+temporary // raises ReferenceError
+permanent // = 10
+permanent2 // = 15
+
+// One of JavaScript's most powerful features is closures. If a function is
+// defined inside another function, the inner function has access to all the
+// outer function's variables.
+function sayHelloInFiveSeconds(name){
+ var prompt = "Hello, " + name + "!"
+ function inner(){
+ alert(prompt)
+ }
+ setTimeout(inner, 5000)
+ // setTimeout is asynchronous, so this function will finish without waiting
+ // 5 seconds. However, once the 5 seconds is up, inner will still have
+ // access to the value of prompt.
+}
+sayHelloInFiveSeconds("Adam") // will open a popup with "Hello, Adam!" in 5s
+
+///////////////////////////////////
+// 5. More about Objects; Constructors and Prototypes
+
+// Objects can contain functions.
+var myObj = {
+ myFunc: function(){
+ return "Hello world!"
+ }
+}
+myObj.myFunc() // = "Hello world!"
+
+// When functions attached to an object are called, they can access the object
+// they're attached to using the this keyword.
+myObj = {
+ myString: "Hello world!",
+ myFunc: function(){
+ return this.myString
+ }
+}
+myObj.myFunc() // = "Hello world!"
+
+// What this is set to has to do with how the function is called, not where
+// it's defined. So, our function doesn't work if it isn't called in the
+// context of the object.
+var myFunc = myObj.myFunc
+myFunc() // = undefined
+
+// Inversely, a function can be assigned to the object and gain access to it
+// through this, even if it wasn't attached when it was defined.
+var myOtherFunc = function(){
+ return this.myString.toUpperCase()
+}
+myObj.myOtherFunc = myOtherFunc
+myObj.myOtherFunc() // = "HELLO WORLD!"
+
+// When you call a function with the new keyword, a new object is created, and
+// made available to the function via this. Functions designed to be called
+// like this are called constructors.
+
+var MyConstructor = function(){
+ this.myNumber = 5
+}
+myNewObj = new MyConstructor() // = {myNumber: 5}
+myNewObj.myNumber // = 5
+
+// Every JavaScript object has a 'prototype'. When you go to access a property
+// on an object that doesn't exist on the actual object, the interpreter will
+// look at its prototype.
+
+// Some JS implementations let you access an object's prototype on the magic
+// property __proto__. While this is useful for explaining prototypes it's not
+// part of the standard; we'll get to standard ways of using prototypes later.
+var myObj = {
+ myString: "Hello world!",
+}
+var myPrototype = {
+ meaningOfLife: 42,
+ myFunc: function(){
+ return this.myString.toLowerCase()
+ }
+}
+myObj.__proto__ = myPrototype
+myObj.meaningOfLife // = 42
+
+// This works for functions, too.
+myObj.myFunc() // = "hello world!"
+
+// Of course, if your property isn't on your prototype, the prototype's
+// prototype is searched, and so on.
+myPrototype.__proto__ = {
+ myBoolean: true
+}
+myObj.myBoolean // = true
+
+// There's no copying involved here; each object stores a reference to its
+// prototype. This means we can alter the prototype and our changes will be
+// reflected everywhere.
+myPrototype.meaningOfLife = 43
+myObj.meaningOfLife // = 43
+
+// We mentioned that __proto__ was non-standard, and there's no standard way to
+// change the prototype of an existing object. However, there's two ways to
+// create a new object with a given prototype.
+
+// The first is Object.create, which is a recent addition to JS, and therefore
+// not available in all implementations yet.
+var myObj = Object.create(myPrototype)
+myObj.meaningOfLife // = 43
+
+// The second way, which works anywhere, has to do with constructors.
+// Constructors have a property called prototype. This is *not* the prototype of
+// the constructor function itself; instead, it's the prototype that new objects
+// are given when they're created with that constructor and the new keyword.
+myConstructor.prototype = {
+ getMyNumber: function(){
+ return this.myNumber
+ }
+}
+var myNewObj2 = new myConstructor()
+myNewObj2.getMyNumber() // = 5
+
+// Built-in types like strings and numbers also have constructors that create
+// equivalent wrapper objects.
+var myNumber = 12
+var myNumberObj = new Number(12)
+myNumber == myNumberObj // = true
+
+// Except, they aren't exactly equivalent.
+typeof(myNumber) // = 'number'
+typeof(myNumberObj) // = 'object'
+myNumber === myNumberObj // = false
+if (0){
+ // This code won't execute, because 0 is falsy.
+}
+if (Number(0)){
+ // This code *will* execute, because Number(0) is truthy.
+}
+
+// However, the wrapper objects and the regular builtins share a prototype, so
+// you can actually add functionality to a string, for instance.
+String.prototype.firstCharacter = function(){
+ return this.charAt(0)
+}
+"abc".firstCharacter() // = "a"
+
+// This fact is often used in "polyfilling", which is implementing newer
+// features of JavaScript in an older subset of JavaScript, so that they can be
+// used in older environments such as outdated browsers.
+
+// For instance, we mentioned that Object.create isn't yet available in all
+// implementations, but we can still use it with this polyfill:
+if (Object.create === undefined){ // don't overwrite it if it exists
+ Object.create = function(proto){
+ // make a temporary constructor with the right prototype
+ var Constructor = function(){}
+ Constructor.prototype = proto
+ // then use it to create a new, appropriately-prototyped object
+ return new Constructor()
+ }
+}
+```
+
+## Further Reading
+
+The [Mozilla Developer
+Network](https://developer.mozilla.org/en-US/docs/Web/JavaScript) provides
+excellent documentation for JavaScript as it's used in browsers. Plus, it's a
+wiki, so as you learn more you can help others out by sharing your own
+knowledge.
+
+MDN's [A re-introduction to
+JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re-introduction_to_JavaScript)
+covers much of the concepts covered here in more detail. This guide has quite
+deliberately only covered the JavaScript language itself; if you want to learn
+more about how to use JavaScript in web pages, start by learning about the
+[Document Object
+Model](https://developer.mozilla.org/en-US/docs/Using_the_W3C_DOM_Level_1_Core)
+
+In addition to direct contributors to this article, some content is adapted
+from Louie Dinh's Python tutorial on this site, and the [JS
+Tutorial](https://developer.mozilla.org/en-US/docs/Web/JavaScript/A_re-introduction_to_JavaScript)
+on the Mozilla Developer Network.
diff --git a/julia.html.markdown b/julia.html.markdown
new file mode 100644
index 00000000..1023e303
--- /dev/null
+++ b/julia.html.markdown
@@ -0,0 +1,525 @@
+---
+language: julia
+contributors:
+ - ["Leah Hanson", "http://leahhanson.us"]
+filename: learnjulia.jl
+---
+
+Julia is a new homoiconic functional language focused on technical computing.
+While having the full power of homoiconic macros, first-class functions, and low-level control, Julia is as easy to learn and use as Python.
+
+This is based on the current development version of Julia, as of June 29th, 2013.
+
+```ruby
+
+# Single line comments start with a hash.
+
+####################################################
+## 1. Primitive Datatypes and Operators
+####################################################
+
+# Everything in Julia is a expression.
+
+# You have numbers
+3 #=> 3 (Int64)
+3.2 #=> 3.2 (Float64)
+2 + 1im #=> 2 + 1im (Complex{Int64})
+2//3 #=> 2//3 (Rational{Int64})
+
+# Math is what you would expect
+1 + 1 #=> 2
+8 - 1 #=> 7
+10 * 2 #=> 20
+35 / 5 #=> 7.0
+5 \ 35 #=> 7.0
+5 / 2 #=> 2.5
+div(5, 2) #=> 2
+2 ^ 2 #=> 4 # power, not bitwise xor
+12 % 10 #=> 2
+
+# Enforce precedence with parentheses
+(1 + 3) * 2 #=> 8
+
+# Bitwise Operators
+~2 #=> -3 # bitwise not
+3 & 5 #=> 1 # bitwise and
+2 | 4 #=> 6 # bitwise or
+2 $ 4 #=> 6 # bitwise xor
+2 >>> 1 #=> 1 # logical shift right
+2 >> 1 #=> 1 # arithmetic shift right
+2 << 1 #=> 4 # logical/arithmetic shift left
+
+# You can use the bits function to see the binary representation of a number.
+bits(12345)
+#=> "0000000000000000000000000000000000000000000000000011000000111001"
+bits(12345.0)
+#=> "0100000011001000000111001000000000000000000000000000000000000000"
+
+# Boolean values are primitives
+true
+false
+
+# Boolean operators
+!true #=> false
+!false #=> true
+1 == 1 #=> true
+2 == 1 #=> false
+1 != 1 #=> false
+2 != 1 #=> true
+1 < 10 #=> true
+1 > 10 #=> false
+2 <= 2 #=> true
+2 >= 2 #=> true
+# Comparisons can be chained
+1 < 2 < 3 #=> true
+2 < 3 < 2 #=> false
+
+# Strings are created with "
+"This is a string."
+
+# Character literals written with '
+'a'
+
+# A string can be treated like a list of characters
+"This is a string"[1] #=> 'T' # Julia indexes from 1
+
+# $ can be used for string interpolation:
+"2 + 2 = $(2 + 2)" #=> "2 + 2 = 4"
+# You can put any Julia expression inside the parenthesis.
+
+# Another way to format strings is the printf macro.
+@printf "%d is less than %f" 4.5 5.3 # 5 is less than 5.300000
+
+####################################################
+## 2. Variables and Collections
+####################################################
+
+# Printing is pretty easy
+println("I'm Julia. Nice to meet you!")
+
+# No need to declare variables before assigning to them.
+some_var = 5 #=> 5
+some_var #=> 5
+
+# Accessing a previously unassigned variable is an error
+try
+ some_other_var #=> ERROR: some_other_var not defined
+catch e
+ println(e)
+end
+
+# Variable name start with a letter. You can use uppercase letters, digits,
+# and exclamation points as well after the initial alphabetic character.
+SomeOtherVar123! = 6 #=> 6
+
+# You can also use unicode characters
+☃ = 8 #=> 8
+
+# A note on naming conventions in Julia:
+#
+# * Names of variables are in lower case, with word separation indicated by
+# underscores ('\_').
+#
+# * Names of Types begin with a capital letter and word separation is shown
+# with CamelCase instead of underscores.
+#
+# * Names of functions and macros are in lower case, without underscores.
+#
+# * Functions that modify their inputs have names that end in !. These
+# functions are sometimes called mutating functions or in-place functions.
+
+# Arrays store a sequence of values indexed by integers 1 through n:
+a = Int64[] #=> 0-element Int64 Array
+
+# 1-dimensional array literals can be written with comma-separated values.
+b = [4, 5, 6] #=> 3-element Int64 Array: [4, 5, 6]
+b[1] #=> 4
+b[end] #=> 6
+
+# 2-dimentional arrays use space-separated values and semicolon-separated rows.
+matrix = [1 2; 3 4] #=> 2x2 Int64 Array: [1 2; 3 4]
+
+# Add stuff to the end of a list with push! and append!
+push!(a,1) #=> [1]
+push!(a,2) #=> [1,2]
+push!(a,4) #=> [1,2,4]
+push!(a,3) #=> [1,2,4,3]
+append!(a,b) #=> [1,2,4,3,4,5,6]
+
+# Remove from the end with pop
+pop!(a) #=> 6 and b is now [4,5]
+
+# Let's put it back
+push!(b,6) # b is now [4,5,6] again.
+
+a[1] #=> 1 # remember that Julia indexes from 1, not 0!
+
+# end is a shorthand for the last index. It can be used in any
+# indexing expression
+a[end] #=> 6
+
+# Function names that end in exclamations points indicate that they modify
+# their argument.
+arr = [5,4,6] #=> 3-element Int64 Array: [5,4,6]
+sort(arr) #=> [4,5,6]; arr is still [5,4,6]
+sort!(arr) #=> [4,5,6]; arr is now [4,5,6]
+
+# Looking out of bounds is a BoundsError
+try
+ a[0] #=> ERROR: BoundsError() in getindex at array.jl:270
+ a[end+1] #=> ERROR: BoundsError() in getindex at array.jl:270
+catch e
+ println(e)
+end
+
+# Errors list the line and file they came from, even if it's in the standard
+# library. If you built Julia from source, you can look in the folder base
+# inside the julia folder to find these files.
+
+# You can initialize arrays from ranges
+a = [1:5] #=> 5-element Int64 Array: [1,2,3,4,5]
+
+# You can look at ranges with slice syntax.
+a[1:3] #=> [1, 2, 3]
+a[2:] #=> [2, 3, 4, 5]
+
+# Remove arbitrary elements from a list with splice!
+arr = [3,4,5]
+splice!(arr,2) #=> 4 ; arr is now [3,5]
+
+# Concatenate lists with append!
+b = [1,2,3]
+append!(a,b) # Now a is [1, 3, 4, 5, 1, 2, 3]
+
+# Check for existence in a list with contains
+contains(a,1) #=> true
+
+# Examine the length with length
+length(a) #=> 7
+
+# Tuples are immutable.
+tup = (1, 2, 3) #=>(1,2,3) # an (Int64,Int64,Int64) tuple.
+tup[1] #=> 1
+try:
+ tup[0] = 3 #=> ERROR: no method setindex!((Int64,Int64,Int64),Int64,Int64)
+catch e
+ println(e)
+end
+
+# Many list functions also work on tuples
+length(tup) #=> 3
+tup[1:2] #=> (1,2)
+contains(tup,2) #=> true
+
+# You can unpack tuples into variables
+a, b, c = (1, 2, 3) #=> (1,2,3) # a is now 1, b is now 2 and c is now 3
+
+# Tuples are created by default if you leave out the parentheses
+d, e, f = 4, 5, 6 #=> (4,5,6)
+
+# Now look how easy it is to swap two values
+e, d = d, e #=> (5,4) # d is now 5 and e is now 4
+
+
+# Dictionaries store mappings
+empty_dict = Dict() #=> Dict{Any,Any}()
+
+# Here is a prefilled dictionary
+filled_dict = ["one"=> 1, "two"=> 2, "three"=> 3]
+# => Dict{ASCIIString,Int64}
+
+# Look up values with []
+filled_dict["one"] #=> 1
+
+# Get all keys
+keys(filled_dict)
+#=> KeyIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
+# Note - dictionary keys are not sorted or in the order you inserted them.
+
+# Get all values
+values(filled_dict)
+#=> ValueIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
+# Note - Same as above regarding key ordering.
+
+# Check for existence of keys in a dictionary with contains, haskey
+contains(filled_dict, ("one", 1)) #=> true
+contains(filled_dict, ("two", 3)) #=> false
+haskey(filled_dict, "one") #=> true
+haskey(filled_dict, 1) #=> false
+
+# Trying to look up a non-existing key will raise an error
+try
+ filled_dict["four"] #=> ERROR: key not found: four in getindex at dict.jl:489
+catch e
+ println(e)
+end
+
+# Use get method to avoid the error
+# get(dictionary,key,default_value)
+get(filled_dict,"one",4) #=> 1
+get(filled_dict,"four",4) #=> 4
+
+# Sets store sets
+empty_set = Set() #=> Set{Any}()
+# Initialize a set with a bunch of values
+filled_set = Set(1,2,2,3,4) #=> Set{Int64}(1,2,3,4)
+
+# Add more items to a set
+add!(filled_set,5) #=> Set{Int64}(5,4,2,3,1)
+
+# There are functions for set intersection, union, and difference.
+other_set = Set(3, 4, 5, 6) #=> Set{Int64}(6,4,5,3)
+intersect(filled_set, other_set) #=> Set{Int64}(3,4,5)
+union(filled_set, other_set) #=> Set{Int64}(1,2,3,4,5,6)
+setdiff(Set(1,2,3,4),Set(2,3,5)) #=> Set{Int64}(1,4)
+
+# Check for existence in a set with contains
+contains(filled_set,2) #=> true
+contains(filled_set,10) #=> false
+
+
+####################################################
+## 3. Control Flow
+####################################################
+
+# Let's make a variable
+some_var = 5
+
+# Here is an if statement. Indentation is NOT meaningful in Julia.
+# prints "some var is smaller than 10"
+if some_var > 10
+ println("some_var is totally bigger than 10.")
+elseif some_var < 10 # This elseif clause is optional.
+ println("some_var is smaller than 10.")
+else # The else clause is optional too.
+ println("some_var is indeed 10.")
+end
+
+
+# For loops iterate over iterables, such as ranges, lists, sets, dicts, strings.
+
+for animal=["dog", "cat", "mouse"]
+ # You can use $ to interpolate into strings
+ println("$animal is a mammal")
+end
+# prints:
+# dog is a mammal
+# cat is a mammal
+# mouse is a mammal
+
+# You can use in instead of =, if you want.
+for animal in ["dog", "cat", "mouse"]
+ println("$animal is a mammal")
+end
+
+for a in ["dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal"]
+ println("$(a[1]) is $(a[2])")
+end
+
+for (k,v) in ["dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal"]
+ println("$k is $v")
+end
+
+
+# While loops go until a condition is no longer met.
+# prints:
+# 0
+# 1
+# 2
+# 3
+x = 0
+while x < 4
+ println(x)
+ x += 1 # Shorthand for x = x + 1
+end
+
+# Handle exceptions with a try/except block
+try
+ error("help")
+catch e
+ println("caught it $e")
+end
+#=> caught it ErrorException("help")
+
+
+####################################################
+## 4. Functions
+####################################################
+
+# Use the keyword function to create new functions
+function add(x, y)
+ println("x is $x and y is $y")
+
+ # Functions implicitly return the value of their last statement
+ x + y
+end
+
+add(5, 6) #=> 11 after printing out "x is 5 and y is 6"
+
+# You can define functions that take a variable number of
+# positional arguments
+function varargs(args...)
+ return args
+end
+
+varargs(1,2,3) #=> (1,2,3)
+
+# The ... is called a splat.
+# It can also be used in a fuction call
+# to splat a list or tuple out to be the arguments
+Set([1,2,3]) #=> Set{Array{Int64,1}}([1,2,3]) # produces a Set of Arrays
+Set([1,2,3]...) #=> Set{Int64}(1,2,3) # this is equivalent to Set(1,2,3)
+
+x = (1,2,3) #=> (1,2,3)
+Set(x) #=> Set{(Int64,Int64,Int64)}((1,2,3)) # a Set of Tuples
+Set(x...) #=> Set{Int64}(2,3,1)
+
+
+# You can define functions with optional positional arguments
+function defaults(a,b,x=5,y=6)
+ return "$a $b and $x $y"
+end
+
+defaults('h','g') #=> "h g and 5 6"
+defaults('h','g','j') #=> "h g and j 6"
+defaults('h','g','j','k') #=> "h g and j k"
+try
+ defaults('h') #=> ERROR: no method defaults(Char,)
+ defaults() #=> ERROR: no methods defaults()
+catch e
+println(e)
+end
+
+# You can define functions that take keyword arguments
+function keyword_args(;k1=4,name2="hello") # note the ;
+ return ["k1"=>k1,"name2"=>name2]
+end
+
+keyword_args(name2="ness") #=> ["name2"=>"ness","k1"=>4]
+keyword_args(k1="mine") #=> ["k1"=>"mine","name2"=>"hello"]
+keyword_args() #=> ["name2"=>"hello","k2"=>4]
+
+# You can also do both at once
+function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo")
+ println("normal arg: $normal_arg")
+ println("optional arg: $optional_positional_arg")
+ println("keyword arg: $keyword_arg")
+end
+
+all_the_args(1, 3, keyword_arg=4)
+# prints:
+# normal arg: 1
+# optional arg: 3
+# keyword arg: 4
+
+# Julia has first class functions
+function create_adder(x)
+ adder = function (y)
+ return x + y
+ end
+ return adder
+end
+
+# or equivalently
+function create_adder(x)
+ y -> x + y
+end
+
+# you can also name the internal function, if you want
+function create_adder(x)
+ function adder(y)
+ x + y
+ end
+ adder
+end
+
+add_10 = create_adder(10)
+add_10(3) #=> 13
+
+# The first two inner functions above are anonymous functions
+(x -> x > 2)(3) #=> true
+
+# There are built-in higher order functions
+map(add_10, [1,2,3]) #=> [11, 12, 13]
+filter(x -> x > 5, [3, 4, 5, 6, 7]) #=> [6, 7]
+
+# We can use list comprehensions for nice maps and filters
+[add_10(i) for i=[1, 2, 3]] #=> [11, 12, 13]
+[add_10(i) for i in [1, 2, 3]] #=> [11, 12, 13]
+
+####################################################
+## 5. Types and Multiple-Dispatch
+####################################################
+
+# Type definition
+type Tiger
+ taillength::Float64
+ coatcolor # no type annotation is implicitly Any
+end
+# default constructor is the properties in order
+# so, Tiger(taillength,coatcolor)
+
+# Type instantiation
+tigger = Tiger(3.5,"orange") # the type doubles as the constructor function
+
+# Abtract Types
+abstract Cat # just a name and point in the type hierarchy
+
+# * types defined with the type keyword are concrete types; they can be
+# instantiated
+#
+# * types defined with the abstract keyword are abstract types; they can
+# have subtypes.
+#
+# * each type has one supertype; a supertype can have zero or more subtypes.
+
+type Lion <: Cat # Lion is a subtype of Cat
+ mane_color
+ roar::String
+end
+
+type Panther <: Cat # Panther is also a subtype of Cat
+ eye_color
+ Panther() = new("green")
+ # Panthers will only have this constructor, and no default constructor.
+end
+
+# Multiple Dispatch
+
+# In Julia, all named functions are generic functions
+# This means that they are built up from many small methods
+# For example, let's make a function meow:
+function meow(cat::Lion)
+ cat.roar # access properties using dot notation
+end
+
+function meow(cat::Panther)
+ "grrr"
+end
+
+function meow(cat::Tiger)
+ "rawwwr"
+end
+
+meow(tigger) #=> "rawwr"
+meow(Lion("brown","ROAAR")) #=> "ROAAR"
+meow(Panther()) #=> "grrr"
+
+function pet_cat(cat::Cat)
+ println("The cat says $(meow(cat))")
+end
+
+try
+ pet_cat(tigger) #=> ERROR: no method pet_cat(Tiger,)
+catch e
+ println(e)
+end
+
+pet_cat(Lion(Panther(),"42")) #=> prints "The cat says 42"
+
+```
+
+## Further Reading
+
+You can get a lot more detail from [The Julia Manual](http://docs.julialang.org/en/latest/manual/)
+
diff --git a/lua.html.markdown b/lua.html.markdown
index 66ebf6bd..0ece399f 100644
--- a/lua.html.markdown
+++ b/lua.html.markdown
@@ -1,7 +1,8 @@
---
language: lua
-author: Tyler Neylon
-author_url: http://tylerneylon.com/
+contributors:
+ - ["Tyler Neylon", "http://tylerneylon.com/"]
+filename: learnlua.lua
---
```lua
diff --git a/php.html.markdown b/php.html.markdown
index 1a8dea2c..9627035c 100644
--- a/php.html.markdown
+++ b/php.html.markdown
@@ -1,7 +1,9 @@
---
language: php
-author: Malcolm Fell
-author_url: http://emarref.net/
+contributors:
+- [Malcolm Fell](http://emarref.net/)
+- [Trismegiste](https://github.com/Trismegiste)
+filename: learnphp.php
---
This document describes PHP 5+.
@@ -9,6 +11,9 @@ This document describes PHP 5+.
```php
<?php // PHP code must be enclosed with <?php ? > tags
+// If your php file only contains PHP code, it is best practise
+// to omit the php closing tag.
+
// Two forward slashes start a one-line comment.
# So will a hash (aka pound symbol) but // is more common
@@ -22,7 +27,7 @@ This document describes PHP 5+.
print('Hello '); // Prints "Hello " with no line break
// () are optional for print and echo
-echo 'World\n'; // Prints "World" with a line break
+echo "World\n"; // Prints "World" with a line break
// (all statements must end with a semicolon)
// Anything outside <?php tags is echoed automatically
@@ -39,13 +44,13 @@ echo 'World\n'; // Prints "World" with a line break
// followed by any number of letters, numbers, or underscores.
// Boolean values are case-insensitive
-$boolean = true; // or TRUE or True
+$boolean = true; // or TRUE or True
$boolean = false; // or FALSE or False
// Integers
-$int1 = 19; // => 19
-$int2 = -19; // => -19
-$int3 = 019; // => 15 (a leading 0 denotes an octal number)
+$int1 = 12; // => 12
+$int2 = -12; // => -12
+$int3 = 012; // => 10 (a leading 0 denotes an octal number)
$int4 = 0x0F; // => 15 (a leading 0x denotes a hex literal)
// Floats (aka doubles)
@@ -54,26 +59,26 @@ $float = 1.2e3;
$float = 7E-10;
// Arithmetic
-$sum = 1 + 1; // 2
+$sum = 1 + 1; // 2
$difference = 2 - 1; // 1
-$product = 2 * 2; // 4
-$quotient = 2 / 1; // 2
+$product = 2 * 2; // 4
+$quotient = 2 / 1; // 2
// Shorthand arithmetic
$number = 0;
-$number += 1; // Add 1 to $number
-echo $number++; // Prints 1 (increments after evaluation)
-echo ++$number; // Prints 3 (increments before evalutation)
+$number += 1; // Increment $number by 1
+echo $number++; // Prints 1 (increments after evaluation)
+echo ++$number; // Prints 3 (increments before evalutation)
$number /= $float; // Divide and assign the quotient to $number
// Strings should be enclosed in single quotes;
$sgl_quotes = '$String'; // => '$String'
// Avoid using double quotes except to embed other variables
-$dbl_quotes = "This is a $sgl_quotes."; // => 'This is a $String'
+$dbl_quotes = "This is a $sgl_quotes."; // => 'This is a $String.'
// Special characters are only escaped in double quotes
-$escaped = "This contains a \t tab character.";
+$escaped = "This contains a \t tab character.";
$unescaped = 'This just contains a slash and a t: \t';
// Enclose a variable in curly braces if needed
@@ -109,7 +114,7 @@ $associative = array('One' => 1, 'Two' => 2, 'Three' => 3);
// PHP 5.4 introduced a new syntax
$associative = ['One' => 1, 'Two' => 2, 'Three' => 3];
-echo $associative['One']; // prints "1"
+echo $associative['One']; // prints 1
// List literals implicitly assign integer keys
$array = ['One', 'Two', 'Three'];
@@ -132,8 +137,8 @@ print 'Hello World!'; // So is print
$paragraph = 'paragraph';
-echo 100;
-echo $paragraph;
+echo 100; // Echo scalar variables directly
+echo $paragraph; // or variables
// If short open tags are configured, or your PHP version is
// 5.4.0 or greater, you can use the short echo syntax
@@ -143,10 +148,11 @@ echo $paragraph;
$x = 1;
$y = 2;
-$x = $y; // A now contains the same value sa $y
+$x = $y; // $x now contains the same value as $y
$z = &$y;
-// $x now contains a reference to $y. Changing the value of
-// $x will change the value of $y also, and vice-versa.
+// $z now contains a reference to $y. Changing the value of
+// $z will change the value of $y also, and vice-versa.
+// $x will remain unchanged as the original value of $y
echo $x; // => 2
echo $z; // => 2
@@ -167,8 +173,8 @@ $d = '1';
// These comparisons will always be true, even if the types aren't the same.
assert($a == $b); // equality
-assert($b != $a); // inequality
-assert($a <> $b); // alternative inequality
+assert($c != $a); // inequality
+assert($c <> $a); // alternative inequality
assert($a < $c);
assert($c > $b);
assert($a <= $b);
@@ -215,7 +221,7 @@ if (true) {
}
if (false) {
- print "I don't";
+ print 'I don\'t';
} else {
print 'I get printed';
}
@@ -226,6 +232,9 @@ if (false) {
print 'Does';
}
+// ternary operator
+print (false ? 'Does not get printed' : 'Does');
+
$x = 0;
if ($x === '0') {
print 'Does not print';
@@ -235,6 +244,8 @@ if ($x === '0') {
print 'Does print';
}
+
+
// This alternative syntax is useful for templates:
?>
@@ -251,6 +262,7 @@ switch ($x) {
case '0':
print 'Switch does type coercion';
break; // You must include a break, or you will fall through
+ // to cases 'two' and 'three'
case 'two':
case 'three':
// Do something if $variable is either 'two' or 'three'
@@ -275,16 +287,16 @@ do {
echo "\n";
for ($x = 0; $x < 10; $x++) {
- echo $x; // Will echo 0 - 9
-}// Prints "0123456789"
+ echo $x;
+} // Prints "0123456789"
echo "\n";
$wheels = ['bicycle' => 2, 'car' => 4];
// Foreach loops can iterate over arrays
-foreach ($wheels as $wheel_count){
- echo "$wheel_count";
+foreach ($wheels as $wheel_count) {
+ echo $wheel_count;
} // Prints "24"
echo "\n";
@@ -302,9 +314,9 @@ while ($i < 5) {
break; // Exit out of the while loop
}
echo $i++;
-}// Prints "012"
+} // Prints "012"
-for($i = 0; $i < 5; $i++){
+for ($i = 0; $i < 5; $i++) {
if ($i === 3) {
continue; // Skip this iteration of the loop
}
@@ -317,7 +329,7 @@ for($i = 0; $i < 5; $i++){
*/
// Define a function with "function":
-function my_function() {
+function my_function () {
return 'Hello';
}
@@ -326,7 +338,7 @@ echo my_function(); // => "Hello"
// A valid function name starts with a letter or underscore, followed by any
// number of letters, numbers, or underscores.
-function add($x, $y = 1) { // $y is optional, and defaults to 2
+function add ($x, $y = 1) { // $y is optional and defaults to 1
$result = $x + $y;
return $result;
}
@@ -338,7 +350,7 @@ echo add(4, 2); // => 6
// print $result; // Gives a warning.
// Since PHP 5.3 you can declare anonymous functions;
-$inc = function($x){
+$inc = function ($x) {
return $x + 1;
};
@@ -357,78 +369,130 @@ function bar ($x, $y) {
}
$bar = bar('A', 'B');
-$bar('C');
+$bar('C'); // Prints "A - B - C"
// You can call named functions using strings
$function_name = 'add';
echo $function_name(1, 2); // => 3
-// But, you should probably use anonymous functions instead.
+// Useful for programatically determining which function to run.
+// Or, use call_user_func(callable $callback [, $parameter [, ... ]]);
+
+/********************************
+ * Includes
+ */
+
+<?php
+// PHP within included files must also begin with a PHP open tag.
+
+include 'my-file.php';
+// The code in my-file.php is now available in the current scope.
+// If the file cannot be included (e.g. file not found), a warning is emitted.
+
+include_once 'my-file.php';
+// If the code in my-file.php has been included elsewhere, it will
+// not be included again. This prevents multiple class declaration errors
+
+require 'my-file.php';
+require_once 'my-file.php';
+// Same as include(), except require() will cause a fatal error if the
+// file cannot be included.
+
+// Contents of my-include.php:
+<?php
+
+return 'Anything you like.';
+// End file
+
+// Includes and requires may also return a value.
+$value = include 'my-include.php';
+
+// Files are included based on the file path given or, if none is given,
+// the include_path configuration directive. If the file isn't found in
+// the include_path, include will finally check in the calling script's
+// own directory and the current working directory before failing.
+/* */
/********************************
* Classes
*/
-//Classes are defined with the class keyword
+// Classes are defined with the class keyword
-class MyClass {
- const MY_CONST = 'value'; // A constant
- static $staticVar = 'static';
- public $property = 'public'; // Properties must declare their visibility
- private $privprop = 'private'; // Accessible within the class only
- protected $protprop = 'protected'; // Accessible within the class and subclasses
+class MyClass
+{
+ const MY_CONST = 'value'; // A constant
+
+ static $staticVar = 'static';
+
+ // Properties must declare their visibility
+ public $property = 'public';
public $instanceProp;
+ protected $prot = 'protected'; // Accessible from the class and subclasses
+ private $priv = 'private'; // Accessible within the class only
// Create a constructor with __construct
- public function __construct($instanceProp){
+ public function __construct($instanceProp) {
// Access instance variables with $this
$this->instanceProp = $instanceProp;
}
+
// Methods are declared as functions inside a class
- public function myMethod() {
- print "MyClass";
+ public function myMethod()
+ {
+ print 'MyClass';
}
- final function youCannotOverrideMe() {
+ final function youCannotOverrideMe()
+ {
}
- public static function myStaticMethod() {
- print "I am static";
+ public static function myStaticMethod()
+ {
+ print 'I am static';
}
}
-echo MyClass::MY_CONST; // Outputs "value";
-echo MyClass::$staticVar; // Outputs 'static';
-MyClass::myStaticMethod(); // Outputs "I am static";
+echo MyClass::MY_CONST; // Outputs 'value';
+echo MyClass::$staticVar; // Outputs 'static';
+MyClass::myStaticMethod(); // Outputs 'I am static';
+
+// Instantiate classes using new
+$my_class = new MyClass('An instance property');
+// The parentheses are optional if not passing in an argument.
-// Access class members using ->.
-$my_class = new MyClass("An instance property"); // The parentheses are optional.
-echo $my_class->property; // => "public"
+// Access class members using ->
+echo $my_class->property; // => "public"
echo $my_class->instanceProp; // => "An instance property"
-$my_class->myMethod(); // => "MyClass"
+$my_class->myMethod(); // => "MyClass"
// Extend classes using "extends"
-class MyOtherClass extends MyClass{
- function printProtectedProperty(){
- echo $this->protprop;
+class MyOtherClass extends MyClass
+{
+ function printProtectedProperty()
+ {
+ echo $this->prot;
}
// Override a method
- function myMethod() {
+ function myMethod()
+ {
parent::myMethod();
- print " > MyOtherClass";
+ print ' > MyOtherClass';
}
}
-$my_other_class = new MyOtherClass("Instance prop");
+$my_other_class = new MyOtherClass('Instance prop');
$my_other_class->printProtectedProperty(); // => Prints "protected"
-$my_other_class->myMethod(); // Prints "MyClass > MyOtherClass"
+$my_other_class->myMethod(); // Prints "MyClass > MyOtherClass"
-final class YouCannotExtendMe {
+final class YouCannotExtendMe
+{
}
// You can use "magic methods" to create getters and setters
-class MyMapClass {
+class MyMapClass
+{
private $property;
public function __get($key)
@@ -460,18 +524,27 @@ interface InterfaceTwo
public function doSomethingElse();
}
+// interfaces can be extended
+interface InterfaceThree extends InterfaceTwo
+{
+ public function doAnotherContract();
+}
+
abstract class MyAbstractClass implements InterfaceOne
{
- public $x = "doSomething";
+ public $x = 'doSomething';
}
class MyConcreteClass extends MyAbstractClass implements InterfaceTwo
{
- public function doSomething(){
+ public function doSomething()
+ {
echo $x;
}
- public function doSomethingElse(){
- echo "doSomethingElse";
+
+ public function doSomethingElse()
+ {
+ echo 'doSomethingElse';
}
}
@@ -479,11 +552,14 @@ class MyConcreteClass extends MyAbstractClass implements InterfaceTwo
// Classes can implement more than one interface
class SomeOtherClass implements InterfaceOne, InterfaceTwo
{
- public function doSomething(){
- echo "doSomething";
+ public function doSomething()
+ {
+ echo 'doSomething';
}
- public function doSomethingElse(){
- echo "doSomethingElse";
+
+ public function doSomethingElse()
+ {
+ echo 'doSomethingElse';
}
}
@@ -492,12 +568,13 @@ class SomeOtherClass implements InterfaceOne, InterfaceTwo
* Traits
*/
-//Traits are available since PHP 5.4.0 and are declared using the trait keyword.
+// Traits are available from PHP 5.4.0 and are declared using "trait"
-trait MyTrait {
+trait MyTrait
+{
public function myTraitMethod()
{
- print "I have MyTrait";
+ print 'I have MyTrait';
}
}
@@ -517,9 +594,6 @@ $cls->myTraitMethod(); // Prints "I have MyTrait"
// This section is separate, because a namespace declaration
// must be the first statement in a file. Let's pretend that is not the case
-/*
-```
-```php
<?php
// By default, classes exist in the global namespace, and can
@@ -565,3 +639,5 @@ Visit the [official PHP documentation](http://www.php.net/manual/) for reference
If you're interested in up-to-date best practices, visit [PHP The Right Way](http://www.phptherightway.com/).
If you're coming from a language with good package management, check out [Composer](http://getcomposer.org/).
+
+For common standards, visit the PHP Framework Interoperability Group's [PSR standards](https://github.com/php-fig/fig-standards).
diff --git a/python.html.markdown b/python.html.markdown
index eddff031..e7ee6fbd 100644
--- a/python.html.markdown
+++ b/python.html.markdown
@@ -1,11 +1,12 @@
---
language: python
-author: Louie Dinh
-author_url: http://ldinh.ca
+contributors:
+ - ["Louie Dinh", "http://ldinh.ca"]
+filename: learnpython.py
---
Python was created by Guido Van Rossum in the early 90's. It is now one of the most popular
-languages in existence. I fell in love with Python for it's syntactic clarity. It's basically
+languages in existence. I fell in love with Python for its syntactic clarity. Its basically
executable pseudocode.
Feedback would be highly appreciated! You can reach me at [@louiedinh](http://twitter.com/louiedinh) or louiedinh [at] [google's email service]
@@ -86,10 +87,26 @@ not False #=> True
# A newer way to format strings is the format method.
# This method is the preferred way
"{0} can be {1}".format("strings", "formatted")
+# You can use keywords if you don't want to count.
+"{name} wants to eat {food}".format(name="Bob", food="lasagna")
# None is an object
None #=> None
+# Don't use the equality `==` symbol to compare objects to None
+# Use `is` instead
+"etc" is None #=> False
+None is None #=> True
+
+# The 'is' operator tests for object identity. This isn't
+# very useful when dealing with primitive values, but is
+# very useful when dealing with objects.
+
+# None, 0, and empty strings/lists all evaluate to False.
+# All other values are True
+0 == False #=> True
+"" == False #=> True
+
####################################################
## 2. Variables and Collections
@@ -103,16 +120,12 @@ print "I'm Python. Nice to meet you!"
some_var = 5 # Convention is to use lower_case_with_underscores
some_var #=> 5
-# Accessing a previously unassigned variable is an exception
-try:
- some_other_var
-except NameError:
- print "Raises a name error"
+# Accessing a previously unassigned variable is an exception.
+# See Control Flow to learn more about exception handling.
+some_other_var # Raises a name error
# if can be used as an expression
-some_var = a if a > b else b
-# If a is greater than b, then a is assigned to some_var.
-# Otherwise b is assigned to some_var.
+"yahoo!" if 3 > 2 else 2 #=> "yahoo!"
# Lists store sequences
li = []
@@ -135,10 +148,7 @@ li[0] #=> 1
li[-1] #=> 3
# Looking out of bounds is an IndexError
-try:
- li[4] # Raises an IndexError
-except IndexError:
- print "Raises an IndexError"
+li[4] # Raises an IndexError
# You can look at ranges with slice syntax.
# (It's a closed/open range for you mathy types.)
@@ -163,13 +173,11 @@ li.extend(other_li) # Now li is [1, 2, 3, 4, 5, 6]
# Examine the length with len
len(li) #=> 6
+
# Tuples are like lists but are immutable.
tup = (1, 2, 3)
tup[0] #=> 1
-try:
- tup[0] = 3 # Raises a TypeError
-except TypeError:
- print "Tuples cannot be mutated."
+tup[0] = 3 # Raises a TypeError
# You can do all those list thingies on tuples too
len(tup) #=> 3
@@ -177,7 +185,7 @@ tup + (4, 5, 6) #=> (1, 2, 3, 4, 5, 6)
tup[:2] #=> (1, 2)
2 in tup #=> True
-# You can unpack tuples into variables
+# You can unpack tuples (or lists) into variables
a, b, c = (1, 2, 3) # a is now 1, b is now 2 and c is now 3
# Tuples are created by default if you leave out the parentheses
d, e, f = 4, 5, 6
@@ -206,13 +214,12 @@ filled_dict.values() #=> [3, 2, 1]
"one" in filled_dict #=> True
1 in filled_dict #=> False
-# Trying to look up a non-existing key will raise a KeyError
-filled_dict["four"] #=> KeyError
+ # Looking up a non-existing key is a KeyError
+filled_dict["four"] # KeyError
# Use get method to avoid the KeyError
filled_dict.get("one") #=> 1
filled_dict.get("four") #=> None
-
# The get method supports a default argument when the value is missing
filled_dict.get("one", 4) #=> 1
filled_dict.get("four", 4) #=> 4
@@ -234,7 +241,7 @@ filled_set = {1, 2, 2, 3, 4} # => {1 2 3 4}
filled_set.add(5) # filled_set is now {1, 2, 3, 4, 5}
# Do set intersection with &
-other_set = set{3, 4, 5, 6}
+other_set = {3, 4, 5, 6}
filled_set & other_set #=> {3, 4, 5}
# Do set union with |
@@ -255,7 +262,7 @@ filled_set | other_set #=> {1, 2, 3, 4, 5, 6}
# Let's just make a variable
some_var = 5
-# Here is an if statement. INDENTATION IS SIGNIFICANT IN PYTHON!
+# Here is an if statement. Indentation is significant in python!
# prints "some var is smaller than 10"
if some_var > 10:
print "some_var is totally bigger than 10."
@@ -275,6 +282,18 @@ prints:
for animal in ["dog", "cat", "mouse"]:
# You can use % to interpolate formatted strings
print "%s is a mammal" % animal
+
+"""
+`range(number)` returns a list of numbers
+from zero to the given number
+prints:
+ 0
+ 1
+ 2
+ 3
+"""
+for i in range(4):
+ print i
"""
While loops go until a condition is no longer met.
@@ -298,12 +317,6 @@ try:
except IndexError as e:
pass # Pass is just a no-op. Usually you would do recovery here.
-# Works for Python 2.7 and down:
-try:
- raise IndexError("This is an index error")
-except IndexError, e: # No "as", comma instead
- pass
-
####################################################
## 4. Functions
@@ -315,7 +328,8 @@ def add(x, y):
return x + y # Return values with a return statement
# Calling functions with parameters
-add(5, 6) #=> 11 and prints out "x is 5 and y is 6"
+add(5, 6) #=> prints out "x is 5 and y is 6" and returns 11
+
# Another way to call functions is with keyword arguments
add(y=6, x=5) # Keyword arguments can arrive in any order.
@@ -341,16 +355,17 @@ def all_the_args(*args, **kwargs):
print kwargs
"""
all_the_args(1, 2, a=3, b=4) prints:
- [1, 2]
+ (1, 2)
{"a": 3, "b": 4}
"""
-# You can also use * and ** when calling a function
+# When calling functions, you can do the opposite of varargs/kwargs!
+# Use * to expand tuples and use ** to expand kwargs.
args = (1, 2, 3, 4)
kwargs = {"a": 3, "b": 4}
-foo(*args) # equivalent to foo(1, 2, 3, 4)
-foo(**kwargs) # equivalent to foo(a=3, b=4)
-foo(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=4)
+all_the_args(*args) # equivalent to foo(1, 2, 3, 4)
+all_the_args(**kwargs) # equivalent to foo(a=3, b=4)
+all_the_args(*args, **kwargs) # equivalent to foo(1, 2, 3, 4, a=3, b=4)
# Python has first class functions
def create_adder(x):
@@ -420,9 +435,47 @@ j.get_species() #=> "H. neanderthalensis"
# Call the static method
Human.grunt() #=> "*grunt*"
+
+
+####################################################
+## 6. Modules
+####################################################
+
+# You can import modules
+import math
+print math.sqrt(16) #=> 4
+
+# You can get specific functions from a module
+from math import ceil, floor
+print ceil(3.7) #=> 4.0
+print floor(3.7) #=> 3.0
+
+# You can import all functions from a module.
+# Warning: this is not recommended
+from math import *
+
+# You can shorten module names
+import math as m
+math.sqrt(16) == m.sqrt(16) #=> True
+
+# Python modules are just ordinary python files. You
+# can write your own, and import them. The name of the
+# module is the same as the name of the file.
+
+# You can find out which functions and attributes
+# defines a module.
+import math
+dir(math)
+
+
```
## Further Reading
-Still up for more? Try [Learn Python The Hard Way](http://learnpythonthehardway.org/book/)
+Still up for more? Try:
+* [Learn Python The Hard Way](http://learnpythonthehardway.org/book/)
+* [Dive Into Python](http://www.diveintopython.net/)
+* [The Official Docs](http://docs.python.org/2.6/)
+* [Hitchhiker's Guide to Python](http://docs.python-guide.org/en/latest/)
+* [Python Module of the Week](http://pymotw.com/2/)
diff --git a/r.html.markdown b/r.html.markdown
index 1ace3ed5..0240e8fb 100644
--- a/r.html.markdown
+++ b/r.html.markdown
@@ -1,11 +1,11 @@
---
language: R
-author: e99n09
-author_url: http://github.com/e99n09
-
+contributors:
+ - ["e99n09", "http://github.com/e99n09"]
+filename: learnr.r
---
-R is a statistical computing language.
+R is a statistical computing language. It has lots of good built-in functions for uploading and cleaning data sets, running common statistical tests, and making graphs. You can also easily compile it within a LaTeX document.
```python
@@ -14,36 +14,30 @@ R is a statistical computing language.
# You can't make a multi-line comment per se,
# but you can stack multiple comments like so.
-# Protip: hit COMMAND-ENTER to execute a line
+# Hit COMMAND-ENTER to execute a line
#########################
# The absolute basics
#########################
-# NUMERICS
+# NUMBERS
-# We've got numbers! Behold the "numeric" class
+# We've got doubles! Behold the "numeric" class
5 # => [1] 5
class(5) # => [1] "numeric"
+# We've also got integers! They look suspiciously similar,
+# but indeed are different
+5L # => [1] 5
+class(5L) # => [1] "integer"
# Try ?class for more information on the class() function
# In fact, you can look up the documentation on just about anything with ?
-# Numerics are like doubles. There's no such thing as integers
-5 == 5.0 # => [1] TRUE
-# Because R doesn't distinguish between integers and doubles,
-# R shows the "integer" form instead of the equivalent "double" form
-# whenever it's convenient:
-5.0 # => [1] 5
-
# All the normal operations!
10 + 66 # => [1] 76
53.2 - 4 # => [1] 49.2
-3.37 * 5.4 # => [1] 18.198
2 * 2.0 # => [1] 4
-3 / 4 # => [1] 0.75
-2.0 / 2 # => [1] 1
+3L / 4 # => [1] 0.75
3 %% 2 # => [1] 1
-4 %% 2 # => [1] 0
# Finally, we've got not-a-numbers! They're numerics too
class(NaN) # => [1] "numeric"
@@ -107,6 +101,17 @@ while (a > 4) {
# Operations on entire vectors (i.e. a whole row, a whole column)
# or apply()-type functions (we'll discuss later) are preferred
+# IF/ELSE
+
+# Again, pretty standard
+if (4 > 3) {
+ print("Huzzah! It worked!")
+} else {
+ print("Noooo! This is blatantly illogical!")
+}
+# =>
+# [1] "Huzzah! It worked!"
+
# FUNCTIONS
# Defined like so:
@@ -126,24 +131,36 @@ myFunc(5) # => [1] 19
# ONE-DIMENSIONAL
# You can vectorize anything, so long as all components have the same type
-vec <- c(4, 5, 6, 7)
-vec # => [1] 4 5 6 7
+vec <- c(8, 9, 10, 11)
+vec # => [1] 8 9 10 11
# The class of a vector is the class of its components
class(vec) # => [1] "numeric"
-# If you vectorize items of different classes, weird coersions happen
+# If you vectorize items of different classes, weird coercions happen
c(TRUE, 4) # => [1] 1 4
c("dog", TRUE, 4) # => [1] "dog" "TRUE" "4"
# We ask for specific components like so (R starts counting from 1)
-vec[1] # => [1] 4
-# We can also search for the indices of specific components
-which(vec %% 2 == 0)
+vec[1] # => [1] 8
+# We can also search for the indices of specific components,
+which(vec %% 2 == 0) # => [1] 1 3
+# or grab just the first or last entry in the vector
+head(vec, 1) # => [1] 8
+tail(vec, 1) # => [1] 11
# If an index "goes over" you'll get NA:
vec[6] # => [1] NA
+# You can find the length of your vector with length()
+length(vec) # => [1] 4
# You can perform operations on entire vectors or subsets of vectors
vec * 4 # => [1] 16 20 24 28
vec[2:3] * 5 # => [1] 25 30
+# and there are many built-in functions to summarize vectors
+mean(vec) # => [1] 9.5
+var(vec) # => [1] 1.666667
+sd(vec) # => [1] 1.290994
+max(vec) # => [1] 11
+min(vec) # => [1] 8
+sum(vec) # => [1] 38
# TWO-DIMENSIONAL (ALL ONE CLASS)
@@ -192,7 +209,7 @@ mat3
# [,1] [,2] [,3] [,4]
# [1,] 1 2 4 5
# [2,] 6 7 0 4
-# Aah, everything of the same class. No coersions. Much better.
+# Aah, everything of the same class. No coercions. Much better.
# TWO-DIMENSIONAL (DIFFERENT CLASSES)
@@ -243,7 +260,8 @@ array(c(c(c(2,300,4),c(8,9,0)),c(c(5,60,0),c(66,7,847))), dim=c(3,2,2))
# LISTS (MULTI-DIMENSIONAL, POSSIBLY RAGGED, OF DIFFERENT TYPES)
# Finally, R has lists (of vectors)
-list1 <- list(time = 1:40, price = c(rnorm(40,.5*list1$time,4))) # random
+list1 <- list(time = 1:40)
+list1$price = c(rnorm(40,.5*list1$time,4)) # random
list1
# You can get items in the list like so
@@ -273,7 +291,8 @@ apply(mat, MAR = 2, myFunc)
# [2,] 7 19
# [3,] 11 23
# Other functions: ?lapply, ?sapply
-# Don't feel too intimiated; everyone agrees they are rather confusing
+
+# Don't feel too intimidated; everyone agrees they are rather confusing
# The plyr package aims to replace (and improve upon!) the *apply() family.
@@ -303,13 +322,13 @@ write.csv(pets, "pets2.csv") # to make a new .csv file
# Scatterplots!
plot(list1$time, list1$price, main = "fake data")
-# Fit a linear model
-myLm <- lm(price ~ time, data = list1)
-myLm # outputs result of regression
+# Regressions!
+linearModel <- lm(price ~ time, data = list1)
+linearModel # outputs result of regression
# Plot regression line on existing plot
-abline(myLm, col = "red")
+abline(linearModel, col = "red")
# Get a variety of nice diagnostics
-plot(myLm)
+plot(linearModel)
# Histograms!
hist(rpois(n = 10000, lambda = 5), col = "thistle")
@@ -325,4 +344,7 @@ require(ggplot2)
```
+## How do I get R?
+* Get R and the R GUI from [http://www.r-project.org/](http://www.r-project.org/)
+* [RStudio](http://www.rstudio.com/ide/) is another GUI
diff --git a/ruby.html.markdown b/ruby.html.markdown
new file mode 100644
index 00000000..af7af918
--- /dev/null
+++ b/ruby.html.markdown
@@ -0,0 +1,313 @@
+---
+language: ruby
+filename: learnruby.rb
+contributors:
+ - ["David Underwood", "http://theflyingdeveloper.com"]
+ - ["Joel Walden", "http://joelwalden.net"]
+---
+
+```ruby
+# This is a comment
+
+=begin
+This is a multiline comment
+No-one uses them
+You shouldn't either
+=end
+
+# First and foremost: Everything is an object.
+
+# Numbers are objects
+
+3.class #=> Fixnum
+
+3.to_s #=> "3"
+
+
+# Some basic arithmetic
+1 + 1 #=> 2
+8 - 1 #=> 7
+10 * 2 #=> 20
+35 / 5 #=> 7
+
+# Special values are objects
+nil # Nothing to see here
+true # truth
+false # falsehood
+
+nil.class #=> NilClass
+true.class #=> TrueClass
+false.class #=> FalseClass
+
+# Equality
+1 == 1 #=> true
+2 == 1 #=> false
+
+# Inequality
+1 != 1 #=> false
+2 != 1 #=> true
+!true #=> false
+!false #=> true
+
+# apart from false itself, nil is the only other 'falsey' value
+
+!nil #=> true
+!false #=> true
+!0 #=> false
+
+# More comparisons
+1 < 10 #=> true
+1 > 10 #=> false
+2 <= 2 #=> true
+2 >= 2 #=> true
+
+# Strings are objects
+
+'I am a string'.class #=> String
+"I am a string too".class #=> String
+
+placeholder = "use string interpolation"
+"I can #{placeholder} when using double quoted strings"
+#=> "I can use string interpolation when using double quoted strings"
+
+
+# print to the output
+puts "I'm printing!"
+
+# Variables
+x = 25 #=> 25
+x #=> 25
+
+# Note that assignment returns the value assigned
+# This means you can do multiple assignment:
+
+x = y = 10 #=> 10
+x #=> 10
+y #=> 10
+
+# By convention, use snake_case for variable names
+snake_case = true
+
+# Use descriptive variable names
+path_to_project_root = '/good/name/'
+path = '/bad/name/'
+
+# Symbols (are objects)
+# Symbols are immutable, reusable constants represented internally by an
+# integer value. They're often used instead of strings to efficiently convey
+# specific, meaningful values
+
+:pending.class #=> Symbol
+
+status = :pending
+
+status == :pending #=> true
+
+status == 'pending' #=> false
+
+status == :approved #=> false
+
+# Arrays
+
+# This is an array
+[1, 2, 3, 4, 5] #=> [1, 2, 3, 4, 5]
+
+# Arrays can contain different types of items
+
+array = [1, "hello", false] #=> => [1, "hello", false]
+
+# Arrays can be indexed
+# From the front
+array[0] #=> 1
+array[12] #=> nil
+
+# From the end
+array[-1] #=> 5
+
+# With a start and end index
+array[2, 4] #=> [3, 4, 5]
+
+# Or with a range
+array[1..3] #=> [2, 3, 4]
+
+# Add to an array like this
+array << 6 #=> [1, 2, 3, 4, 5, 6]
+
+# Hashes are Ruby's primary dictionary with keys/value pairs.
+# Hashes are denoted with curly braces:
+hash = {'color' => 'green', 'number' => 5}
+
+hash.keys #=> ['color', 'number']
+
+# Hashes can be quickly looked up by key:
+hash['color'] #=> 'green'
+hash['number'] #=> 5
+
+# Asking a hash for a key that doesn't exist returns nil:
+hash['nothing here'] #=> nil
+
+# Iterate over hashes with the #each method:
+hash.each do |k, v|
+ puts "#{k} is #{v}"
+end
+
+# Since Ruby 1.9, there's a special syntax when using symbols as keys:
+
+new_hash = { defcon: 3, action: true}
+
+new_hash.keys #=> [:defcon, :action]
+
+# Tip: Both Arrays and Hashes are Enumerable
+# They share a lot of useful methods such as each, map, count, and more
+
+# Control structures
+
+if true
+ "if statement"
+elsif false
+ "else if, optional"
+else
+ "else, also optional"
+end
+
+for counter in 1..5
+ puts "iteration #{counter}"
+end
+#=> iteration 1
+#=> iteration 2
+#=> iteration 3
+#=> iteration 4
+#=> iteration 5
+
+# HOWEVER
+# No-one uses for loops
+# Use `each` instead, like this:
+
+(1..5).each do |counter|
+ puts "iteration #{counter}"
+end
+#=> iteration 1
+#=> iteration 2
+#=> iteration 3
+#=> iteration 4
+#=> iteration 5
+
+counter = 1
+while counter <= 5 do
+ puts "iteration #{counter}"
+ counter += 1
+end
+#=> iteration 1
+#=> iteration 2
+#=> iteration 3
+#=> iteration 4
+#=> iteration 5
+
+grade = 'B'
+
+case grade
+when 'A'
+ puts "Way to go kiddo"
+when 'B'
+ puts "Better luck next time"
+when 'C'
+ puts "You can do better"
+when 'D'
+ puts "Scraping through"
+when 'F'
+ puts "You failed!"
+else
+ puts "Alternative grading system, eh?"
+end
+
+# Functions
+
+def double(x)
+ x * 2
+end
+
+# Functions (and all blocks) implcitly return the value of the last statement
+double(2) #=> 4
+
+# Parentheses are optional where the result is unambiguous
+double 3 #=> 6
+
+double double 3 #=> 12
+
+def sum(x,y)
+ x + y
+end
+
+# Method arguments are separated by a comma
+sum 3, 4 #=> 7
+
+sum sum(3,4), 5 #=> 12
+
+# yield
+# All methods have an implicit, optional block parameter
+# it can be called with the 'yield' keyword
+
+def surround
+ puts "{"
+ yield
+ puts "}"
+end
+
+surround { puts 'hello world' }
+
+# {
+# hello world
+# }
+
+
+# Define a class with the class keyword
+class Human
+
+ # A class variable. It is shared by all instances of this class.
+ @@species = "H. sapiens"
+
+ # Basic initializer
+ def initialize(name, age=0)
+ # Assign the argument to the "name" instance variable for the instance
+ @name = name
+ # If no age given, we will fall back to the default in the arguments list.
+ @age = age
+ end
+
+ # Basic setter method
+ def name=(name)
+ @name = name
+ end
+
+ # Basic getter method
+ def name
+ @name
+ end
+
+ # A class method uses self to distinguish from instance methods.
+ # It can only be called on the class, not an instance.
+ def self.say(msg)
+ puts "#{msg}"
+ end
+
+ def species
+ @@species
+ end
+
+end
+
+
+# Instantiate a class
+jim = Human.new("Jim Halpert")
+
+dwight = Human.new("Dwight K. Schrute")
+
+# Let's call a couple of methods
+jim.species #=> "H. sapiens"
+jim.name #=> "Jim Halpert"
+dwight.species #=> "H. sapiens"
+dwight.name #=> "Dwight K. Schrute"
+
+# Call the class method
+Human.say("Hi") #=> "Hi"
+```