diff options
Diffstat (limited to 'julia.html.markdown')
| -rw-r--r-- | julia.html.markdown | 212 |
1 files changed, 106 insertions, 106 deletions
diff --git a/julia.html.markdown b/julia.html.markdown index a71870be..e5706062 100644 --- a/julia.html.markdown +++ b/julia.html.markdown @@ -33,27 +33,27 @@ This is based on Julia 1.0.0 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 # 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 +~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 bitstring function to see the binary representation of a number. bitstring(12345) @@ -66,7 +66,7 @@ true false # Boolean operators -!true # => false +!true # => false !false # => true 1 == 1 # => true 2 == 1 # => false @@ -172,17 +172,17 @@ matrix = [1 2; 3 4] # => 2x2 Int64 Array: [1 2; 3 4] 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! @@ -191,14 +191,14 @@ a[1] # => 1 # remember that Julia indexes from 1, not 0! a[end] # => 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] +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] +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 @@ -221,20 +221,20 @@ 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, 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) @@ -243,12 +243,12 @@ catch e end # Many list functions also work on tuples -length(tup) # => 3 +length(tup) # => 3 tup[1:2] # => (1,2) -in(2, tup) # => true +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) @@ -258,11 +258,11 @@ d, e, f = 4, 5, 6 # => (4,5,6) (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) @@ -282,10 +282,10 @@ values(filled_dict) # 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 @@ -296,26 +296,26 @@ 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) #################################################### @@ -409,15 +409,15 @@ 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(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 @@ -427,16 +427,16 @@ 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 @@ -444,24 +444,24 @@ 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 ; +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") @@ -485,7 +485,7 @@ 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) @@ -501,12 +501,12 @@ 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] @@ -519,11 +519,11 @@ 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. @@ -544,10 +544,10 @@ 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. @@ -559,32 +559,32 @@ 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) # 4-element Array{Any,1}: +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(SubString) # => AbstractString +supertype(SubString) # => AbstractString # <: is the subtyping operator struct Lion <: Cat # Lion is a subtype of Cat @@ -631,9 +631,9 @@ 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 Tiger <: Cat # => false @@ -645,9 +645,9 @@ 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 @@ -662,21 +662,21 @@ function fight(t::Tiger, c::Cat) 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 (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(Lion("balooga!"), Panther()) # => prints The victorious cat says grrr +fight(Lion("balooga!"), Panther()) # => prints The victorious cat says grrr try fight(Panther(), Lion("RAWR")) catch e @@ -689,7 +689,7 @@ 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) @@ -697,7 +697,7 @@ 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(Lion("RAR"), Lion("brown", "rarrr")) # => prints The lions come to a tie # Under the hood @@ -705,7 +705,7 @@ fight(Lion("RAR"), Lion("brown", "rarrr")) # => prints The lions come to a tie 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,)) @@ -746,7 +746,7 @@ code_native(square_area, (Float64,)) # 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 |