diff options
| -rw-r--r-- | bash.html.markdown | 10 | ||||
| -rw-r--r-- | c++.html.markdown | 3 | ||||
| -rw-r--r-- | haskell.html.markdown | 2 | ||||
| -rw-r--r-- | python.html.markdown | 10 | ||||
| -rw-r--r-- | standard-ml.html.markdown | 24 |
5 files changed, 38 insertions, 11 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index 35bed9a2..e0c12f97 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -10,6 +10,7 @@ contributors: - ["Anton Strömkvist", "http://lutic.org/"] - ["Rahil Momin", "https://github.com/iamrahil"] - ["Gregrory Kielian", "https://github.com/gskielian"] + - ["Etan Reisner", "https://github.com/deryni"] filename: LearnBash.sh --- @@ -36,7 +37,14 @@ VARIABLE="Some string" # But not like this: VARIABLE = "Some string" # Bash will decide that VARIABLE is a command it must execute and give an error -# because it couldn't be found. +# because it can't be found. + +# Or like this: +VARIABLE= 'Some string' +# Bash will decide that 'Some string' is a command it must execute and give an +# error because it can't be found. (In this case the 'VARIABLE=' part is seen +# as a variable assignment valid only for the scope of the 'Some string' +# command.) # Using the variable: echo $VARIABLE diff --git a/c++.html.markdown b/c++.html.markdown index 1a84efa4..ae93ceba 100644 --- a/c++.html.markdown +++ b/c++.html.markdown @@ -32,8 +32,7 @@ one of the most widely-used programming languages. // variable declarations, primitive types, and functions. // Just like in C, your program's entry point is a function called -// main with an integer return type, -// though void main() is also accepted by most compilers (gcc, clang, etc.) +// main with an integer return type. // This value serves as the program's exit status. // See http://en.wikipedia.org/wiki/Exit_status for more information. int main(int argc, char** argv) diff --git a/haskell.html.markdown b/haskell.html.markdown index f28fcfe7..6a64442f 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -282,7 +282,7 @@ foldl (\x y -> 2*x + y) 4 [1,2,3] -- 43 foldr (\x y -> 2*x + y) 4 [1,2,3] -- 16 -- This is now the same as -(2 * 3 + (2 * 2 + (2 * 1 + 4))) +(2 * 1 + (2 * 2 + (2 * 3 + 4))) ---------------------------------------------------- -- 7. Data Types diff --git a/python.html.markdown b/python.html.markdown index 7281a330..ace3f794 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -46,7 +46,7 @@ to Python 2.x. For Python 3.x, take a look at the [Python 3 tutorial](http://lea 2.0 # This is a float 11.0 / 4.0 # => 2.75 ahhh...much better -# Result of integer division truncated down both for positive and negative. +# Result of integer division truncated down both for positive and negative. 5 // 3 # => 1 5.0 // 3.0 # => 1.0 # works on floats too -5 // 3 # => -2 @@ -191,14 +191,14 @@ li[2:] # => [4, 3] li[:3] # => [1, 2, 4] # Select every second entry li[::2] # =>[1, 4] -# Revert the list +# Reverse a copy of the list li[::-1] # => [3, 4, 2, 1] # Use any combination of these to make advanced slices # li[start:end:step] # Remove arbitrary elements from a list with "del" del li[2] # li is now [1, 2, 3] - +r # You can add lists li + other_li # => [1, 2, 3, 4, 5, 6] # Note: values for li and for other_li are not modified. @@ -439,14 +439,14 @@ def pass_all_the_args(*args, **kwargs): print varargs(*args) print keyword_args(**kwargs) -# Function Scope +# Function Scope x = 5 def setX(num): # Local var x not the same as global variable x x = num # => 43 print x # => 43 - + def setGlobalX(num): global x print x # => 5 diff --git a/standard-ml.html.markdown b/standard-ml.html.markdown index b545f3e1..07896beb 100644 --- a/standard-ml.html.markdown +++ b/standard-ml.html.markdown @@ -3,13 +3,14 @@ language: "Standard ML" contributors: - ["Simon Shine", "http://shine.eu.org/"] - ["David Pedersen", "http://lonelyproton.com/"] + - ["James Baker", "http://www.jbaker.io/"] --- Standard ML is a functional programming language with type inference and some side-effects. Some of the hard parts of learning Standard ML are: Recursion, pattern matching, type inference (guessing the right types but never allowing -implicit type conversion). If you have an imperative background, not being able -to update variables can feel severely inhibiting. +implicit type conversion). Standard ML is distinguished from Haskell by including +references, allowing variables to be updated. ```ocaml (* Comments in Standard ML begin with (* and end with *). Comments can be @@ -383,6 +384,25 @@ val test_poem = readPoem "roses.txt" (* gives [ "Roses are red,", "Violets are blue.", "I have a gun.", "Get in the van." ] *) + +(* We can create references to data which can be updated *) +val counter = ref 0 (* Produce a reference with the ref function *) + +(* Assign to a reference with the assignment operator *) +fun set_five reference = reference := 5 + +(* Read a reference with the dereference operator *) +fun equals_five reference = !reference = 5 + +(* We can use while loops for when recursion is messy *) +fun decrement_to_zero r = if !r < 0 + then r := 0 + else while !r >= 0 do r := !r - 1 + +(* This returns the unit value (in practical terms, nothing, a 0-tuple) *) + +(* To allow returning a value, we can use the semicolon to sequence evaluations *) +fun decrement_ret x y = (x := !x - 1; y) ``` ## Further learning |