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Diffstat (limited to 'julia.html.markdown')
| -rw-r--r-- | julia.html.markdown | 318 |
1 files changed, 159 insertions, 159 deletions
diff --git a/julia.html.markdown b/julia.html.markdown index b8e24b39..8245e616 100644 --- a/julia.html.markdown +++ b/julia.html.markdown @@ -21,58 +21,58 @@ This is based on the current development version of Julia, as of October 18th, 2 # Everything in Julia is a 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 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 # 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 -2 $ 4 #=> 6 # bitwise xor -2 >>> 1 #=> 1 # logical shift right -2 >> 1 #=> 1 # arithmetic shift right -2 << 1 #=> 4 # logical/arithmetic shift left +~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" +# => "0000000000000000000000000000000000000000000000000011000000111001" bits(12345.0) -#=> "0100000011001000000111001000000000000000000000000000000000000000" +# => "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 +!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 " "This is a string." @@ -81,12 +81,12 @@ false 'a' # A string can be indexed like an array of characters -"This is a string"[1] #=> 'T' # Julia indexes from 1 +"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" +"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. @@ -100,24 +100,24 @@ println("I'm Julia. Nice to meet you!") #################################################### # 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: some_other_var not defined catch e println(e) end # Variable names start with a letter. # After that, you can use letters, digits, underscores, and exclamation points. -SomeOtherVar123! = 6 #=> 6 +SomeOtherVar123! = 6 # => 6 # You can also use unicode characters -☃ = 8 #=> 8 +☃ = 8 # => 8 # These are especially handy for mathematical notation -2 * π #=> 6.283185307179586 +2 * π # => 6.283185307179586 # A note on naming conventions in Julia: # @@ -133,49 +133,49 @@ 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[1] #=> 4 -b[end] #=> 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] +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] +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. -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] +shift!(a) # => 1 and a is now [2,4,3,4,5,6] +unshift!(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] # => ERROR: BoundsError() in getindex at array.jl:270 + a[end+1] # => ERROR: BoundsError() in getindex at array.jl:270 catch e println(e) end @@ -185,110 +185,110 @@ 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] -a[2:] #=> [2, 3, 4, 5] -a[2:end] #=> [2, 3, 4, 5] +a[1:3] # => [1, 2, 3] +a[2:] # => [2, 3, 4, 5] +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] # 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 +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] = 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 +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 = ["one"=> 1, "two"=> 2, "three"=> 3] # => Dict{ASCIIString,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]) +# => 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]) +# => 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 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-existant key will raise an error try - filled_dict["four"] #=> ERROR: key not found: four in getindex at dict.jl:489 + filled_dict["four"] # => ERROR: key not found: four in getindex at dict.jl:489 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(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{Int64}(1,2,3,4) # Add more values to a set -push!(filled_set,5) #=> Set{Int64}(5,4,2,3,1) +push!(filled_set,5) # => Set{Int64}(5,4,2,3,1) # 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{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) #################################################### @@ -306,7 +306,7 @@ elseif some_var < 10 # This elseif clause is optional. else # The else clause is optional too. println("some_var is indeed 10.") end -#=> prints "some var is smaller than 10" +# => prints "some var is smaller than 10" # For loops iterate over iterables. @@ -363,7 +363,7 @@ try catch e println("caught it $e") end -#=> caught it ErrorException("help") +# => caught it ErrorException("help") #################################################### @@ -381,7 +381,7 @@ function add(x, y) x + y end -add(5, 6) #=> 11 after printing out "x is 5 and y is 6" +add(5, 6) # => 11 after printing out "x is 5 and y is 6" # You can define functions that take a variable number of # positional arguments @@ -389,20 +389,20 @@ function varargs(args...) return args # use the keyword return to return anywhere in the function end -#=> varargs (generic function with 1 method) +# => varargs (generic function with 1 method) -varargs(1,2,3) #=> (1,2,3) +varargs(1,2,3) # => (1,2,3) # The ... is called a splat. # We just used it in a function definition. # It can also be used in a fuction call, # where it will splat an Array or Tuple's contents into the argument list. -Set([1,2,3]) #=> Set{Array{Int64,1}}([1,2,3]) # produces a Set of Arrays -Set([1,2,3]...) #=> Set{Int64}(1,2,3) # this is equivalent to Set(1,2,3) +Set([1,2,3]) # => Set{Array{Int64,1}}([1,2,3]) # produces a Set of Arrays +Set([1,2,3]...) # => Set{Int64}(1,2,3) # this is equivalent to Set(1,2,3) -x = (1,2,3) #=> (1,2,3) -Set(x) #=> Set{(Int64,Int64,Int64)}((1,2,3)) # a Set of Tuples -Set(x...) #=> Set{Int64}(2,3,1) +x = (1,2,3) # => (1,2,3) +Set(x) # => Set{(Int64,Int64,Int64)}((1,2,3)) # a Set of Tuples +Set(x...) # => Set{Int64}(2,3,1) # You can define functions with optional positional arguments @@ -410,12 +410,12 @@ function defaults(a,b,x=5,y=6) return "$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 @@ -425,9 +425,9 @@ 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","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") @@ -451,7 +451,7 @@ 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) @@ -467,16 +467,16 @@ 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] -[add_10(i) for i in [1, 2, 3]] #=> [11, 12, 13] +[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 @@ -485,11 +485,11 @@ 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. @@ -510,10 +510,10 @@ 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. @@ -524,23 +524,23 @@ abstract Cat # just a name and point in the type hierarchy # Abstract types cannot be instantiated, but can have subtypes. # For example, Number is an abstract type -subtypes(Number) #=> 6-element Array{Any,1}: +subtypes(Number) # => 6-element Array{Any,1}: # Complex{Float16} # Complex{Float32} # Complex{Float64} # Complex{T<:Real} # ImaginaryUnit # Real -subtypes(Cat) #=> 0-element Array{Any,1} +subtypes(Cat) # => 0-element Array{Any,1} # Every type has a super type; use the `super` function to get it. -typeof(5) #=> Int64 -super(Int64) #=> Signed -super(Signed) #=> Real -super(Real) #=> Number -super(Number) #=> Any -super(super(Signed)) #=> Number -super(Any) #=> Any +typeof(5) # => Int64 +super(Int64) # => Signed +super(Signed) # => Real +super(Real) # => Number +super(Number) # => Any +super(super(Signed)) # => Number +super(Any) # => Any # All of these type, except for Int64, are abstract. # <: is the subtyping operator @@ -588,23 +588,23 @@ function meow(animal::Tiger) 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 +issubtype(Tiger,Cat) # => false +issubtype(Lion,Cat) # => true +issubtype(Panther,Cat) # => true # Defining a function that takes Cats function pet_cat(cat::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 @@ -617,31 +617,31 @@ end function fight(t::Tiger,c::Cat) println("The $(t.coatcolor) tiger wins!") end -#=> fight (generic function with 1 method) +# => 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 (generic function with 2 methods) +# => 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 (generic function with 3 methods) +# => 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")) #=> ERROR: no method fight(Panther,Lion) + fight(Panther(),Lion("RAWR")) # => ERROR: no method fight(Panther,Lion) catch end # Also let the cat go first fight(c::Cat,l::Lion) = println("The cat beats the Lion") -#=> Warning: New definition +# => Warning: New definition # fight(Cat,Lion) at none:1 # is ambiguous with # fight(Lion,Cat) at none:2. @@ -651,11 +651,11 @@ fight(c::Cat,l::Lion) = println("The cat beats the Lion") #fight (generic function with 4 methods) # This warning is because it's unclear which fight will be called in: -fight(Lion("RAR"),Lion("brown","rarrr")) #=> prints The victorious cat says rarrr +fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr # 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(Lion("RAR"),Lion("brown","rarrr")) # => prints The lions come to a tie # Under the hood |