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-rw-r--r--julia.html.markdown590
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diff --git a/julia.html.markdown b/julia.html.markdown
index a30871eb..891a0a00 100644
--- a/julia.html.markdown
+++ b/julia.html.markdown
@@ -2,17 +2,17 @@
language: Julia
contributors:
- ["Leah Hanson", "http://leahhanson.us"]
- - ["Pranit Bauva", "http://github.com/pranitbauva1997"]
- - ["Daniel YC Lin", "http://github.com/dlintw"]
+ - ["Pranit Bauva", "https://github.com/pranitbauva1997"]
+ - ["Daniel YC Lin", "https://github.com/dlintw"]
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 Julia 0.6.4
+This is based on Julia 1.0.0
-```ruby
+```julia
# Single line comments start with a hash (pound) symbol.
#= Multiline comments can be written
@@ -27,38 +27,38 @@ This is based on Julia 0.6.4
# Everything in Julia is an expression.
# There are several basic types of numbers.
-3 # => 3 (Int64)
-3.2 # => 3.2 (Float64)
-2 + 1im # => 2 + 1im (Complex{Int64})
-2//3 # => 2//3 (Rational{Int64})
+3 # => 3 (Int64)
+3.2 # => 3.2 (Float64)
+2 + 1im # => 2 + 1im (Complex{Int64})
+2 // 3 # => 2 // 3 (Rational{Int64})
# All of the normal infix operators are available.
-1 + 1 # => 2
-8 - 1 # => 7
-10 * 2 # => 20
-35 / 5 # => 7.0
-5 / 2 # => 2.5 # dividing an Int by an Int always results in a Float
-div(5, 2) # => 2 # for a truncated result, use div
-5 \ 35 # => 7.0
-2 ^ 2 # => 4 # power, not bitwise xor
-12 % 10 # => 2
+1 + 1 # => 2
+8 - 1 # => 7
+10 * 2 # => 20
+35 / 5 # => 7.0
+5 / 2 # => 2.5 # dividing integers always results in a Float64
+div(5, 2) # => 2 # for a truncated result, use div
+5 \ 35 # => 7.0
+2^2 # => 4 # power, not bitwise xor
+12 % 10 # => 2
# Enforce precedence with parentheses
-(1 + 3) * 2 # => 8
+(1 + 3) * 2 # => 8
# Bitwise Operators
-~2 # => -3 # bitwise not
-3 & 5 # => 1 # bitwise and
-2 | 4 # => 6 # bitwise or
-xor(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)
+~2 # => -3 # bitwise not
+3 & 5 # => 1 # bitwise and
+2 | 4 # => 6 # bitwise or
+xor(2, 4) # => 6 # bitwise xor
+2 >>> 1 # => 1 # logical shift right
+2 >> 1 # => 1 # arithmetic shift right
+2 << 1 # => 4 # logical/arithmetic shift left
+
+# Use the bitstring function to see the binary representation of a number.
+bitstring(12345)
# => "0000000000000000000000000000000000000000000000000011000000111001"
-bits(12345.0)
+bitstring(12345.0)
# => "0100000011001000000111001000000000000000000000000000000000000000"
# Boolean values are primitives
@@ -66,48 +66,38 @@ 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
+!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
+1 < 2 < 3 # => true
+2 < 3 < 2 # => false
# Strings are created with "
-try
"This is a string."
-catch ; end
-
-# Julia has several types of strings, including ASCIIString and UTF8String.
-# More on this in the Types section.
# Character literals are written with '
-try
'a'
-catch ; end
-# Some strings can be indexed like an array of characters
-try
-"This is a string"[1] # => 'T' # Julia indexes from 1
-catch ; end
-# However, this is will not work well for UTF8 strings,
-# so iterating over strings is recommended (map, for loops, etc).
+# Strings are UTF8 encoded. Only if they contain only ASCII characters can
+# they be safely indexed.
+ascii("This is a string")[1] # => 'T' # Julia indexes from 1
+# Otherwise, iterating over strings is recommended (map, for loops, etc).
# $ can be used for string interpolation:
-try
"2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
-catch ; end
# You can put any Julia expression inside the parentheses.
-# Another way to format strings is the printf macro.
-@printf "%d is less than %f" 4.5 5.3 # 4 is less than 5.300000
+# Another way to format strings is the printf macro from the stdlib Printf.
+using Printf
+@printf "%d is less than %f\n" 4.5 5.3 # => 5 is less than 5.300000
# Printing is easy
println("I'm Julia. Nice to meet you!")
@@ -115,29 +105,29 @@ println("I'm Julia. Nice to meet you!")
# String can be compared lexicographically
"good" > "bye" # => true
"good" == "good" # => true
-"1 + 2 = 3" == "1 + 2 = $(1+2)" # => true
+"1 + 2 = 3" == "1 + 2 = $(1 + 2)" # => true
####################################################
## 2. Variables and Collections
####################################################
# You don't declare variables before assigning to them.
-some_var = 5 # => 5
-some_var # => 5
+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
+ some_other_var # => ERROR: UndefVarError: some_other_var not defined
catch e
println(e)
end
# Variable names start with a letter or underscore.
# After that, you can use letters, digits, underscores, and exclamation points.
-SomeOtherVar123! = 6 # => 6
+SomeOtherVar123! = 6 # => 6
# You can also use certain unicode characters
-☃ = 8 # => 8
+☃ = 8 # => 8
# These are especially handy for mathematical notation
2 * π # => 6.283185307179586
@@ -156,165 +146,168 @@ SomeOtherVar123! = 6 # => 6
# 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
+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 = [4; 5; 6] # => 3-element Int64 Array: [4, 5, 6]
-b[1] # => 4
-b[end] # => 6
+b = [4, 5, 6] # => 3-element Int64 Array: [4, 5, 6]
+b = [4; 5; 6] # => 3-element Int64 Array: [4, 5, 6]
+b[1] # => 4
+b[end] # => 6
# 2-dimensional arrays use space-separated values and semicolon-separated rows.
-matrix = [1 2; 3 4] # => 2x2 Int64 Array: [1 2; 3 4]
+matrix = [1 2; 3 4] # => 2x2 Int64 Array: [1 2; 3 4]
-# Arrays of a particular Type
-b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6]
+# Arrays of a particular type
+b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6]
# 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]
+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!(b) # => 6 and b is now [4,5]
+pop!(b) # => 6 and b is now [4,5]
# Let's put it back
-push!(b,6) # b is now [4,5,6] again.
+push!(b, 6) # b is now [4,5,6] again.
-a[1] # => 1 # remember that Julia indexes from 1, not 0!
+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
+a[end] # => 6
-# we also have shift and unshift
-shift!(a) # => 1 and a is now [2,4,3,4,5,6]
-unshift!(a,7) # => [7,2,4,3,4,5,6]
+# we also have popfirst! and pushfirst!
+popfirst!(a) # => 1 and a is now [2,4,3,4,5,6]
+pushfirst!(a, 7) # => [7,2,4,3,4,5,6]
# 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]
+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
+ a[0]
+ # => BoundsError: attempt to access 7-element Array{Int64,1} at index [0]
+ a[end + 1]
+ # => BoundsError: attempt to access 7-element Array{Int64,1} at index [8]
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.
+# library. You can look in the folder share/julia 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]
+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:end] # => [2, 3, 4, 5]
+a[1:3] # => [1, 2, 3]
+a[2:end] # => [2, 3, 4, 5]
# Remove elements from an array by index with splice!
arr = [3,4,5]
-splice!(arr,2) # => 4 ; arr is now [3,5]
+splice!(arr, 2) # => 4 ; arr is now [3,5]
# Concatenate lists with append!
b = [1,2,3]
-append!(a,b) # Now a is [1, 2, 3, 4, 5, 1, 2, 3]
+append!(a, b) # Now a is [1, 2, 3, 4, 5, 1, 2, 3]
# Check for existence in a list with in
-in(1, a) # => true
+in(1, a) # => true
# Examine the length with length
-length(a) # => 8
+length(a) # => 8
# Tuples are immutable.
-tup = (1, 2, 3) # => (1,2,3) # an (Int64,Int64,Int64) tuple.
-tup[1] # => 1
-try:
- tup[1] = 3 # => ERROR: no method setindex!((Int64,Int64,Int64),Int64,Int64)
+tup = (1, 2, 3) # => (1,2,3) # an (Int64,Int64,Int64) tuple.
+tup[1] # => 1
+try
+ tup[1] = 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)
-in(2, tup) # => true
+# Many array functions also work on tuples
+length(tup) # => 3
+tup[1:2] # => (1,2)
+in(2, tup) # => 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
+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 even if you leave out the parentheses
-d, e, f = 4, 5, 6 # => (4,5,6)
+d, e, f = 4, 5, 6 # => (4,5,6)
# A 1-element tuple is distinct from the value it contains
-(1,) == 1 # => false
-(1) == 1 # => true
+(1,) == 1 # => false
+(1) == 1 # => true
# Look how easy it is to swap two values
-e, d = d, e # => (5,4) # d is now 5 and e is now 4
+e, d = d, e # => (5,4) # d is now 5 and e is now 4
# Dictionaries store mappings
-empty_dict = Dict() # => Dict{Any,Any}()
+empty_dict = Dict() # => Dict{Any,Any}()
# You can create a dictionary using a literal
-filled_dict = Dict("one"=> 1, "two"=> 2, "three"=> 3)
-# => Dict{ASCIIString,Int64}
+filled_dict = Dict("one" => 1, "two" => 2, "three" => 3)
+# => Dict{String,Int64}
# Look up values with []
-filled_dict["one"] # => 1
+filled_dict["one"] # => 1
# Get all keys
keys(filled_dict)
-# => KeyIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
+# => Base.KeySet for a Dict{String,Int64} with 3 entries. Keys:
+# "two", "one", "three"
# 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])
+# => Base.ValueIterator{Dict{String,Int64}} with 3 entries. Values: 2, 1, 3
# Note - Same as above regarding key ordering.
# Check for existence of keys in a dictionary with in, haskey
-in(("one" => 1), filled_dict) # => true
-in(("two" => 3), filled_dict) # => false
-haskey(filled_dict, "one") # => true
-haskey(filled_dict, 1) # => false
+in(("one" => 1), filled_dict) # => true
+in(("two" => 3), filled_dict) # => false
+haskey(filled_dict, "one") # => true
+haskey(filled_dict, 1) # => false
# Trying to look up a non-existent key will raise an error
try
- filled_dict["four"] # => ERROR: key not found: four in getindex at dict.jl:489
+ filled_dict["four"] # => KeyError: key "four" not found
catch e
println(e)
end
# Use the get method to avoid that error by providing a default value
-# get(dictionary,key,default_value)
-get(filled_dict,"one",4) # => 1
-get(filled_dict,"four",4) # => 4
+# get(dictionary, key, default_value)
+get(filled_dict, "one", 4) # => 1
+get(filled_dict, "four", 4) # => 4
# Use Sets to represent collections of unordered, unique values
-empty_set = Set() # => Set{Any}()
+empty_set = Set() # => Set{Any}()
# Initialize a set with values
-filled_set = Set([1,2,2,3,4]) # => Set{Int64}(1,2,3,4)
+filled_set = Set([1, 2, 2, 3, 4]) # => Set([4, 2, 3, 1])
# Add more values to a set
-push!(filled_set,5) # => Set{Int64}(5,4,2,3,1)
+push!(filled_set, 5) # => Set([4, 2, 3, 5, 1])
# Check if the values are in the set
-in(2, filled_set) # => true
-in(10, filled_set) # => false
+in(2, filled_set) # => true
+in(10, filled_set) # => false
# 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)
+other_set = Set([3, 4, 5, 6]) # => Set([4, 3, 5, 6])
+intersect(filled_set, other_set) # => Set([4, 3, 5])
+union(filled_set, other_set) # => Set([4, 2, 3, 5, 6, 1])
+setdiff(Set([1,2,3,4]), Set([2,3,5])) # => Set([4, 1])
####################################################
@@ -337,7 +330,7 @@ end
# For loops iterate over iterables.
# Iterable types include Range, Array, Set, Dict, and AbstractString.
-for animal=["dog", "cat", "mouse"]
+for animal = ["dog", "cat", "mouse"]
println("$animal is a mammal")
# You can use $ to interpolate variables or expression into strings
end
@@ -355,15 +348,16 @@ end
# cat is a mammal
# mouse is a mammal
-for a in Dict("dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal")
- println("$(a[1]) is a $(a[2])")
+for pair in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
+ from, to = pair
+ println("$from is a $to")
end
# prints:
# dog is a mammal
# cat is a mammal
# mouse is a mammal
-for (k,v) in Dict("dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal")
+for (k, v) in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
println("$k is a $v")
end
# prints:
@@ -372,10 +366,11 @@ end
# mouse is a mammal
# While loops loop while a condition is true
-x = 0
-while x < 4
- println(x)
- x += 1 # Shorthand for x = x + 1
+let x = 0
+ while x < 4
+ println(x)
+ x += 1 # Shorthand for x = x + 1
+ end
end
# prints:
# 0
@@ -385,9 +380,9 @@ end
# Handle exceptions with a try/catch block
try
- error("help")
+ error("help")
catch e
- println("caught it $e")
+ println("caught it $e")
end
# => caught it ErrorException("help")
@@ -407,15 +402,15 @@ function add(x, y)
x + y
end
-add(5, 6) # => 11 after printing out "x is 5 and y is 6"
+add(5, 6) # => 11 after printing out "x is 5 and y is 6"
# Compact assignment of functions
-f_add(x, y) = x + y # => "f (generic function with 1 method)"
-f_add(3, 4) # => 7
+f_add(x, y) = x + y # => "f (generic function with 1 method)"
+f_add(3, 4) # => 7
# Function can also return multiple values as tuple
fn(x, y) = x + y, x - y
-fn(3, 4) # => (7, -1)
+fn(3, 4) # => (7, -1)
# You can define functions that take a variable number of
# positional arguments
@@ -425,41 +420,41 @@ function varargs(args...)
end
# => varargs (generic function with 1 method)
-varargs(1,2,3) # => (1,2,3)
+varargs(1, 2, 3) # => (1,2,3)
# The ... is called a splat.
# We just used it in a function definition.
# It can also be used in a function call,
# where it will splat an Array or Tuple's contents into the argument list.
-add([5,6]...) # this is equivalent to add(5,6)
+add([5,6]...) # this is equivalent to add(5,6)
-x = (5,6) # => (5,6)
-add(x...) # this is equivalent to add(5,6)
+x = (5, 6) # => (5,6)
+add(x...) # this is equivalent to add(5,6)
# You can define functions with optional positional arguments
-function defaults(a,b,x=5,y=6)
+function defaults(a, b, x=5, y=6)
return "$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"
+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()
+ 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 Dict("k1"=>k1,"name2"=>name2)
+function keyword_args(;k1=4, name2="hello") # note the ;
+ return Dict("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","k1"=>4]
+keyword_args(name2="ness") # => ["name2"=>"ness","k1"=>4]
+keyword_args(k1="mine") # => ["k1"=>"mine","name2"=>"hello"]
+keyword_args() # => ["name2"=>"hello","k1"=>4]
# You can combine all kinds of arguments in the same function
function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo")
@@ -483,7 +478,7 @@ function create_adder(x)
end
# This is "stabby lambda syntax" for creating anonymous functions
-(x -> x > 2)(3) # => true
+(x -> x > 2)(3) # => true
# This function is identical to create_adder implementation above.
function create_adder(x)
@@ -499,16 +494,17 @@ function create_adder(x)
end
add_10 = create_adder(10)
-add_10(3) # => 13
+add_10(3) # => 13
# 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]
+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 nicer maps
-[add_10(i) for i=[1, 2, 3]] # => [11, 12, 13]
+# We can use list comprehensions
+[add_10(i) for i = [1, 2, 3]] # => [11, 12, 13]
[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
+[x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7]
####################################################
## 5. Types
@@ -517,11 +513,11 @@ filter(x -> x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
# Julia has a type system.
# Every value has a type; variables do not have types themselves.
# You can use the `typeof` function to get the type of a value.
-typeof(5) # => Int64
+typeof(5) # => Int64
# Types are first-class values
-typeof(Int64) # => DataType
-typeof(DataType) # => DataType
+typeof(Int64) # => DataType
+typeof(DataType) # => DataType
# DataType is the type that represents types, including itself.
# Types are used for documentation, optimizations, and dispatch.
@@ -529,78 +525,77 @@ typeof(DataType) # => DataType
# Users can define types
# They are like records or structs in other languages.
-# New types are defined using the `type` keyword.
+# New types are defined using the `struct` keyword.
-# type Name
+# struct Name
# field::OptionalType
# ...
# end
-type Tiger
- taillength::Float64
- coatcolor # not including a type annotation is the same as `::Any`
+struct Tiger
+ taillength::Float64
+ coatcolor # not including a type annotation is the same as `::Any`
end
# The default constructor's arguments are the properties
# of the type, in the order they are listed in the definition
-tigger = Tiger(3.5,"orange") # => Tiger(3.5,"orange")
+tigger = Tiger(3.5, "orange") # => Tiger(3.5,"orange")
# The type doubles as the constructor function for values of that type
-sherekhan = typeof(tigger)(5.6,"fire") # => Tiger(5.6,"fire")
+sherekhan = typeof(tigger)(5.6, "fire") # => Tiger(5.6,"fire")
# These struct-style types are called concrete types
# They can be instantiated, but cannot have subtypes.
# The other kind of types is abstract types.
# abstract Name
-abstract type Cat end # just a name and point in the type hierarchy
+abstract type Cat end # just a name and point in the type hierarchy
# Abstract types cannot be instantiated, but can have subtypes.
+using InteractiveUtils # defines the subtype and supertype function
# For example, Number is an abstract type
-subtypes(Number) # => 2-element Array{Any,1}:
+subtypes(Number) # => 2-element Array{Any,1}:
# Complex{T<:Real}
# Real
-subtypes(Cat) # => 0-element Array{Any,1}
+subtypes(Cat) # => 0-element Array{Any,1}
# AbstractString, as the name implies, is also an abstract type
-subtypes(AbstractString) # 6-element Array{Union{DataType, UnionAll},1}:
- # Base.SubstitutionString
- # Base.Test.GenericString
- # DirectIndexString
- # RevString
- # String
- # SubString
+subtypes(AbstractString) # 4-element Array{Any,1}:
+ # String
+ # SubString
+ # SubstitutionString
+ # Test.GenericString
# Every type has a super type; use the `supertype` function to get it.
-typeof(5) # => Int64
-supertype(Int64) # => Signed
-supertype(Signed) # => Integer
-supertype(Integer) # => Real
-supertype(Real) # => Number
-supertype(Number) # => Any
-supertype(supertype(Signed)) # => Real
-supertype(Any) # => Any
+typeof(5) # => Int64
+supertype(Int64) # => Signed
+supertype(Signed) # => Integer
+supertype(Integer) # => Real
+supertype(Real) # => Number
+supertype(Number) # => Any
+supertype(supertype(Signed)) # => Real
+supertype(Any) # => Any
# All of these type, except for Int64, are abstract.
-typeof("fire") # => String
-supertype(String) # => AbstractString
+typeof("fire") # => String
+supertype(String) # => AbstractString
# Likewise here with String
-supertype(DirectIndexString) # => AbstractString
+supertype(SubString) # => AbstractString
# <: is the subtyping operator
-type Lion <: Cat # Lion is a subtype of Cat
- mane_color
- roar::AbstractString
+struct Lion <: Cat # Lion is a subtype of Cat
+ mane_color
+ roar::AbstractString
end
# You can define more constructors for your type
# Just define a function of the same name as the type
# and call an existing constructor to get a value of the correct type
-Lion(roar::AbstractString) = Lion("green",roar)
+Lion(roar::AbstractString) = Lion("green", roar)
# This is an outer constructor because it's outside the type definition
-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.
+struct 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
# Using inner constructors, like Panther does, gives you control
# over how values of the type can be created.
@@ -618,35 +613,35 @@ end
# Definitions for Lion, Panther, Tiger
function meow(animal::Lion)
- animal.roar # access type properties using dot notation
+ animal.roar # access type properties using dot notation
end
function meow(animal::Panther)
- "grrr"
+ "grrr"
end
function meow(animal::Tiger)
- "rawwwr"
+ "rawwwr"
end
# Testing the meow function
-meow(tigger) # => "rawwr"
-meow(Lion("brown","ROAAR")) # => "ROAAR"
-meow(Panther()) # => "grrr"
+meow(tigger) # => "rawwr"
+meow(Lion("brown", "ROAAR")) # => "ROAAR"
+meow(Panther()) # => "grrr"
# Review the local type hierarchy
-issubtype(Tiger,Cat) # => false
-issubtype(Lion,Cat) # => true
-issubtype(Panther,Cat) # => true
+Tiger <: Cat # => false
+Lion <: Cat # => true
+Panther <: Cat # => true
# Defining a function that takes Cats
function pet_cat(cat::Cat)
- println("The cat says $(meow(cat))")
+ println("The cat says $(meow(cat))")
end
-pet_cat(Lion("42")) # => prints "The cat says 42"
+pet_cat(Lion("42")) # => prints "The cat says 42"
try
- pet_cat(tigger) # => ERROR: no method pet_cat(Tiger,)
+ pet_cat(tigger) # => ERROR: no method pet_cat(Tiger,)
catch e
println(e)
end
@@ -656,129 +651,132 @@ end
# In Julia, all of the argument types contribute to selecting the best method.
# Let's define a function with more arguments, so we can see the difference
-function fight(t::Tiger,c::Cat)
- println("The $(t.coatcolor) tiger wins!")
+function fight(t::Tiger, c::Cat)
+ println("The $(t.coatcolor) tiger wins!")
end
# => fight (generic function with 1 method)
-fight(tigger,Panther()) # => prints The orange tiger wins!
-fight(tigger,Lion("ROAR")) # => prints The orange tiger wins!
+fight(tigger, Panther()) # => prints The orange tiger wins!
+fight(tigger, Lion("ROAR")) # => prints The orange tiger wins!
# Let's change the behavior when the Cat is specifically a Lion
-fight(t::Tiger,l::Lion) = println("The $(l.mane_color)-maned lion wins!")
+fight(t::Tiger, l::Lion) = println("The $(l.mane_color)-maned lion wins!")
# => fight (generic function with 2 methods)
-fight(tigger,Panther()) # => prints The orange tiger wins!
-fight(tigger,Lion("ROAR")) # => prints The green-maned lion wins!
+fight(tigger, Panther()) # => prints The orange tiger wins!
+fight(tigger, Lion("ROAR")) # => prints The green-maned lion wins!
# We don't need a Tiger in order to fight
-fight(l::Lion,c::Cat) = println("The victorious cat says $(meow(c))")
+fight(l::Lion, c::Cat) = println("The victorious cat says $(meow(c))")
# => fight (generic function with 3 methods)
-fight(Lion("balooga!"),Panther()) # => prints The victorious cat says grrr
+fight(Lion("balooga!"), Panther()) # => prints The victorious cat says grrr
try
- fight(Panther(),Lion("RAWR"))
+ fight(Panther(), Lion("RAWR"))
catch e
- println(e)
- # => MethodError(fight, (Panther("green"), Lion("green", "RAWR")), 0x000000000000557b)
+ println(e)
+ # => MethodError(fight, (Panther("green"), Lion("green", "RAWR")),
+ # 0x000000000000557b)
end
# Also let the cat go first
-fight(c::Cat,l::Lion) = println("The cat beats the Lion")
+fight(c::Cat, l::Lion) = println("The cat beats the Lion")
# This warning is because it's unclear which fight will be called in:
try
- fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr
+ fight(Lion("RAR"), Lion("brown", "rarrr"))
+ # => prints The victorious cat says rarrr
catch e
- println(e)
- # => MethodError(fight, (Lion("green", "RAR"), Lion("brown", "rarrr")), 0x000000000000557c)
+ println(e)
+ # => MethodError(fight, (Lion("green", "RAR"), Lion("brown", "rarrr")),
+ # 0x000000000000557c)
end
# The result may be different in other versions of Julia
-fight(l::Lion,l2::Lion) = println("The lions come to a tie")
-fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The lions come to a tie
+fight(l::Lion, l2::Lion) = println("The lions come to a tie")
+fight(Lion("RAR"), Lion("brown", "rarrr")) # => prints The lions come to a tie
# Under the hood
# You can take a look at the llvm and the assembly code generated.
-square_area(l) = l * l # square_area (generic function with 1 method)
+square_area(l) = l * l # square_area (generic function with 1 method)
-square_area(5) #25
+square_area(5) # => 25
# What happens when we feed square_area an integer?
code_native(square_area, (Int32,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1 # Prologue
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # movsxd RAX, EDI # Fetch l from memory?
- # imul RAX, RAX # Square l and store the result in RAX
- # pop RBP # Restore old base pointer
- # ret # Result will still be in RAX
+ # .section __TEXT,__text,regular,pure_instructions
+ # Filename: none
+ # Source line: 1 # Prologue
+ # push RBP
+ # mov RBP, RSP
+ # Source line: 1
+ # movsxd RAX, EDI # Fetch l from memory?
+ # imul RAX, RAX # Square l and store the result in RAX
+ # pop RBP # Restore old base pointer
+ # ret # Result will still be in RAX
code_native(square_area, (Float32,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # vmulss XMM0, XMM0, XMM0 # Scalar single precision multiply (AVX)
- # pop RBP
- # ret
+ # .section __TEXT,__text,regular,pure_instructions
+ # Filename: none
+ # Source line: 1
+ # push RBP
+ # mov RBP, RSP
+ # Source line: 1
+ # vmulss XMM0, XMM0, XMM0 # Scalar single precision multiply (AVX)
+ # pop RBP
+ # ret
code_native(square_area, (Float64,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # vmulsd XMM0, XMM0, XMM0 # Scalar double precision multiply (AVX)
- # pop RBP
- # ret
- #
+ # .section __TEXT,__text,regular,pure_instructions
+ # Filename: none
+ # Source line: 1
+ # push RBP
+ # mov RBP, RSP
+ # Source line: 1
+ # vmulsd XMM0, XMM0, XMM0 # Scalar double precision multiply (AVX)
+ # pop RBP
+ # ret
+ #
# Note that julia will use floating point instructions if any of the
# arguments are floats.
# Let's calculate the area of a circle
circle_area(r) = pi * r * r # circle_area (generic function with 1 method)
-circle_area(5) # 78.53981633974483
+circle_area(5) # 78.53981633974483
code_native(circle_area, (Int32,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # vcvtsi2sd XMM0, XMM0, EDI # Load integer (r) from memory
- # movabs RAX, 4593140240 # Load pi
- # vmulsd XMM1, XMM0, QWORD PTR [RAX] # pi * r
- # vmulsd XMM0, XMM0, XMM1 # (pi * r) * r
- # pop RBP
- # ret
- #
+ # .section __TEXT,__text,regular,pure_instructions
+ # Filename: none
+ # Source line: 1
+ # push RBP
+ # mov RBP, RSP
+ # Source line: 1
+ # vcvtsi2sd XMM0, XMM0, EDI # Load integer (r) from memory
+ # movabs RAX, 4593140240 # Load pi
+ # vmulsd XMM1, XMM0, QWORD PTR [RAX] # pi * r
+ # vmulsd XMM0, XMM0, XMM1 # (pi * r) * r
+ # pop RBP
+ # ret
+ #
code_native(circle_area, (Float64,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # movabs RAX, 4593140496
- # Source line: 1
- # vmulsd XMM1, XMM0, QWORD PTR [RAX]
- # vmulsd XMM0, XMM1, XMM0
- # pop RBP
- # ret
- #
+ # .section __TEXT,__text,regular,pure_instructions
+ # Filename: none
+ # Source line: 1
+ # push RBP
+ # mov RBP, RSP
+ # movabs RAX, 4593140496
+ # Source line: 1
+ # vmulsd XMM1, XMM0, QWORD PTR [RAX]
+ # vmulsd XMM0, XMM1, XMM0
+ # pop RBP
+ # ret
+ #
```
## Further Reading
-You can get a lot more detail from [The Julia Manual](http://docs.julialang.org/en/latest/#Manual-1)
+You can get a lot more detail from the [Julia Documentation](https://docs.julialang.org/)
The best place to get help with Julia is the (very friendly) [Discourse forum](https://discourse.julialang.org/).