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Diffstat (limited to 'julia.html.markdown')
| -rw-r--r-- | julia.html.markdown | 77 |
1 files changed, 57 insertions, 20 deletions
diff --git a/julia.html.markdown b/julia.html.markdown index e9d3a162..2810555e 100644 --- a/julia.html.markdown +++ b/julia.html.markdown @@ -1,20 +1,21 @@ --- -language: julia +language: Julia contributors: - ["Leah Hanson", "http://leahhanson.us"] + - ["Pranit Bauva", "http://github.com/pranitbauva1997"] 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 October 18th, 2013. +This is based on Julia 0.3. ```ruby -# Single line comments start with a number symbol. +# Single line comments start with a hash (pound) symbol. #= Multiline comments can be written - by putting '#=' before the text and '=#' + by putting '#=' before the text and '=#' after the text. They can also be nested. =# @@ -81,17 +82,20 @@ false # Strings are created with " "This is a string." +# Julia has several types of strings, including ASCIIString and UTF8String. +# More on this in the Types section. + # Character literals are written with ' 'a' -# A string can be indexed like an array of characters +# Some strings can be indexed like an array of characters "This is a string"[1] # => 'T' # Julia indexes from 1 # However, this is will not work well for UTF8 strings, # so iterating over strings is recommended (map, for loops, etc). # $ can be used for string interpolation: "2 + 2 = $(2 + 2)" # => "2 + 2 = 4" -# You can put any Julia expression inside the parenthesis. +# 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 # 5 is less than 5.300000 @@ -99,6 +103,11 @@ false # Printing is easy 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 + #################################################### ## 2. Variables and Collections #################################################### @@ -114,19 +123,20 @@ catch e println(e) end -# Variable names start with a letter. +# Variable names start with a letter or underscore. # After that, you can use letters, digits, underscores, and exclamation points. SomeOtherVar123! = 6 # => 6 -# You can also use unicode characters +# You can also use certain unicode characters ☃ = 8 # => 8 # These are especially handy for mathematical notation 2 * π # => 6.283185307179586 # A note on naming conventions in Julia: # -# * Names of variables are in lower case, with word separation indicated by -# underscores ('\_'). +# * Word separation can be indicated by underscores ('_'), but use of +# underscores is discouraged unless the name would be hard to read +# otherwise. # # * Names of Types begin with a capital letter and word separation is shown # with CamelCase instead of underscores. @@ -141,12 +151,16 @@ 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 # 2-dimentional arrays use space-separated values and semicolon-separated rows. 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] + # Add stuff to the end of a list with push! and append! push!(a,1) # => [1] push!(a,2) # => [1,2] @@ -189,7 +203,7 @@ end # 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] @@ -263,7 +277,7 @@ in(("two", 3), filled_dict) # => false haskey(filled_dict, "one") # => true haskey(filled_dict, 1) # => false -# Trying to look up a non-existant key will raise an error +# 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 catch e @@ -313,7 +327,7 @@ end # For loops iterate over iterables. -# Iterable types include Range, Array, Set, Dict, and String. +# Iterable types include Range, Array, Set, Dict, and AbstractString. for animal=["dog", "cat", "mouse"] println("$animal is a mammal") # You can use $ to interpolate variables or expression into strings @@ -386,6 +400,14 @@ end 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 + +# Function can also return multiple values as tuple +f(x, y) = x + y, x - y +f(3, 4) # => (7, -1) + # You can define functions that take a variable number of # positional arguments function varargs(args...) @@ -536,6 +558,17 @@ subtypes(Number) # => 6-element Array{Any,1}: # Real subtypes(Cat) # => 0-element Array{Any,1} +# AbstractString, as the name implies, is also an abstract type +subtypes(AbstractString) # 8-element Array{Any,1}: + # Base.SubstitutionString{T<:AbstractString} + # DirectIndexString + # RepString + # RevString{T<:AbstractString} + # RopeString + # SubString{T<:AbstractString} + # UTF16String + # UTF8String + # Every type has a super type; use the `super` function to get it. typeof(5) # => Int64 super(Int64) # => Signed @@ -545,17 +578,21 @@ super(Number) # => Any super(super(Signed)) # => Number super(Any) # => Any # All of these type, except for Int64, are abstract. +typeof("fire") # => ASCIIString +super(ASCIIString) # => DirectIndexString +super(DirectIndexString) # => AbstractString +# Likewise here with ASCIIString # <: is the subtyping operator type Lion <: Cat # Lion is a subtype of Cat mane_color - roar::String + 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::String) = 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 @@ -669,7 +706,7 @@ square_area(l) = l * l # square_area (generic function with 1 method) square_area(5) #25 # What happens when we feed square_area an integer? -code_native(square_area, (Int32,)) +code_native(square_area, (Int32,)) # .section __TEXT,__text,regular,pure_instructions # Filename: none # Source line: 1 # Prologue @@ -702,10 +739,10 @@ code_native(square_area, (Float64,)) # vmulsd XMM0, XMM0, XMM0 # Scalar double precision multiply (AVX) # pop RBP # ret - # + # # Note that julia will use floating point instructions if any of the -# arguements are floats. -# Let's calculate the area of a circle +# 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 @@ -736,7 +773,7 @@ code_native(circle_area, (Float64,)) # vmulsd XMM0, XMM1, XMM0 # pop RBP # ret - # + # ``` ## Further Reading |