diff options
| -rw-r--r-- | julia.html.markdown | 317 |
1 files changed, 194 insertions, 123 deletions
diff --git a/julia.html.markdown b/julia.html.markdown index dfa3103c..416f1a5a 100644 --- a/julia.html.markdown +++ b/julia.html.markdown @@ -89,7 +89,9 @@ false # 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 +ascii("This is a string")[1] +# => 'T': ASCII/Unicode U+0054 (category Lu: Letter, uppercase) +# Julia indexes from 1 # Otherwise, iterating over strings is recommended (map, for loops, etc). # $ can be used for string interpolation: @@ -101,7 +103,7 @@ 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!") +println("I'm Julia. Nice to meet you!") # => I'm Julia. Nice to meet you! # String can be compared lexicographically "good" > "bye" # => true @@ -147,19 +149,18 @@ 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 Array{Int64,1} # 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 = [4, 5, 6] # => 3-element Array{Int64,1}: [4, 5, 6] +b = [4; 5; 6] # => 3-element Array{Int64,1}: [4, 5, 6] 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] # => 2×2 Array{Int64,2}: [1 2; 3 4] # Arrays of a particular type -b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6] +b = Int8[4, 5, 6] # => 3-element Array{Int8,1}: [4, 5, 6] # Add stuff to the end of a list with push! and append! push!(a, 1) # => [1] @@ -186,16 +187,28 @@ 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 Array{Int64,1}: [5,4,6] # Looking out of bounds is a BoundsError try - 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] + a[0] + # => ERROR: BoundsError: attempt to access 7-element Array{Int64,1} at + # index [0] + # => Stacktrace: + # => [1] getindex(::Array{Int64,1}, ::Int64) at .\array.jl:731 + # => [2] top-level scope at none:0 + # => [3] ... + # => in expression starting at ...\LearnJulia.jl:180 + a[end + 1] + # => ERROR: BoundsError: attempt to access 7-element Array{Int64,1} at + # index [8] + # => Stacktrace: + # => [1] getindex(::Array{Int64,1}, ::Int64) at .\array.jl:731 + # => [2] top-level scope at none:0 + # => [3] ... + # => in expression starting at ...\LearnJulia.jl:188 catch e println(e) end @@ -205,7 +218,8 @@ end # 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 Array{Int64,1}: [1,2,3,4,5] +a2 = [1:5] # => 1-element Array{UnitRange{Int64},1}: [1:5] # You can look at ranges with slice syntax. a[1:3] # => [1, 2, 3] @@ -229,7 +243,9 @@ length(a) # => 8 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: MethodError: no method matching + # setindex!(::Tuple{Int64,Int64,Int64}, ::Int64, ::Int64) catch e println(e) end @@ -254,11 +270,12 @@ 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} with 0 entries # You can create a dictionary using a literal filled_dict = Dict("one" => 1, "two" => 2, "three" => 3) -# => Dict{String,Int64} +# => Dict{String,Int64} with 3 entries: +# => "two" => 2, "one" => 1, "three" => 3 # Look up values with [] filled_dict["one"] # => 1 @@ -266,12 +283,13 @@ filled_dict["one"] # => 1 # Get all keys keys(filled_dict) # => Base.KeySet for a Dict{String,Int64} with 3 entries. Keys: -# "two", "one", "three" +# => "two", "one", "three" # Note - dictionary keys are not sorted or in the order you inserted them. # Get all values values(filled_dict) -# => Base.ValueIterator{Dict{String,Int64}} with 3 entries. Values: 2, 1, 3 +# => Base.ValueIterator for a 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 @@ -282,7 +300,7 @@ haskey(filled_dict, 1) # => false # Trying to look up a non-existent key will raise an error try - filled_dict["four"] # => KeyError: key "four" not found + filled_dict["four"] # => ERROR: KeyError: key "four" not found catch e println(e) end @@ -293,7 +311,7 @@ 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([4, 2, 3, 1]) @@ -353,18 +371,16 @@ for pair in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal") from, to = pair println("$from is a $to") end -# prints: -# dog is a mammal -# cat is a mammal -# mouse is a mammal +# => mouse is a mammal +# => cat is a mammal +# => dog is a mammal for (k, v) in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal") println("$k is a $v") end -# prints: -# dog is a mammal -# cat is a mammal -# mouse is a mammal +# => mouse is a mammal +# => cat is a mammal +# => dog is a mammal # While loops loop while a condition is true let x = 0 @@ -406,11 +422,11 @@ end add(5, 6) # => 11 after printing out "x is 5 and y is 6" # Compact assignment of functions -f_add(x, y) = x + y # => "f (generic function with 1 method)" +f_add(x, y) = x + y # => f_add (generic function with 1 method) f_add(3, 4) # => 7 # Function can also return multiple values as tuple -fn(x, y) = x + y, x - y +fn(x, y) = x + y, x - y # => fn (generic function with 1 method) fn(3, 4) # => (7, -1) # You can define functions that take a variable number of @@ -437,13 +453,14 @@ add(x...) # this is equivalent to add(5,6) function defaults(a, b, x=5, y=6) return "$a $b and $x $y" end +# => defaults (generic function with 3 methods) 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: MethodError: no method matching defaults(::Char) + defaults() # => ERROR: MethodError: no method matching defaults() catch e println(e) end @@ -452,10 +469,11 @@ end function keyword_args(;k1=4, name2="hello") # note the ; return Dict("k1" => k1, "name2" => name2) end +# => keyword_args (generic function with 1 method) -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") # => ["name2"=>"hello", "k1"=>"mine"] +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") @@ -463,6 +481,7 @@ function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo") println("optional arg: $optional_positional_arg") println("keyword arg: $keyword_arg") end +# => all_the_args (generic function with 2 methods) all_the_args(1, 3, keyword_arg=4) # prints: @@ -477,6 +496,7 @@ function create_adder(x) end return adder end +# => create_adder (generic function with 1 method) # This is "stabby lambda syntax" for creating anonymous functions (x -> x > 2)(3) # => true @@ -485,6 +505,7 @@ end function create_adder(x) y -> x + y end +# => create_adder (generic function with 1 method) # You can also name the internal function, if you want function create_adder(x) @@ -493,9 +514,11 @@ function create_adder(x) end adder end +# => create_adder (generic function with 1 method) -add_10 = create_adder(10) -add_10(3) # => 13 +add_10 = create_adder(10) # => (::getfield(Main, Symbol("#adder#11")){Int64}) + # (generic function with 1 method) +add_10(3) # => 13 # There are built-in higher order functions @@ -555,16 +578,16 @@ abstract type Cat end # just a name and point in the type hierarchy using InteractiveUtils # defines the subtype and supertype function # For example, Number is an abstract type subtypes(Number) # => 2-element Array{Any,1}: - # Complex{T<:Real} - # Real + # => Complex + # => Real subtypes(Cat) # => 0-element Array{Any,1} # AbstractString, as the name implies, is also an abstract type -subtypes(AbstractString) # 4-element Array{Any,1}: - # String - # SubString - # SubstitutionString - # Test.GenericString +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 @@ -626,7 +649,7 @@ function meow(animal::Tiger) end # Testing the meow function -meow(tigger) # => "rawwr" +meow(tigger) # => "rawwwr" meow(Lion("brown", "ROAAR")) # => "ROAAR" meow(Panther()) # => "grrr" @@ -639,10 +662,11 @@ Panther <: Cat # => true function pet_cat(cat::Cat) println("The cat says $(meow(cat))") end +# => pet_cat (generic function with 1 method) -pet_cat(Lion("42")) # => prints "The cat says 42" +pet_cat(Lion("42")) # => The cat says 42 try - pet_cat(tigger) # => ERROR: no method pet_cat(Tiger,) + pet_cat(tigger) # => ERROR: MethodError: no method matching pet_cat(::Tiger) catch e println(e) end @@ -657,45 +681,54 @@ 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()) # => The orange tiger wins! +fight(tigger, Lion("ROAR")) # => 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()) # => The orange tiger wins! +fight(tigger, Lion("ROAR")) # => 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()) # => The victorious cat says grrr try - fight(Panther(), Lion("RAWR")) + fight(Panther(), Lion("RAWR")) + # => ERROR: MethodError: no method matching fight(::Panther, ::Lion) + # => Closest candidates are: + # => fight(::Tiger, ::Lion) at ... + # => fight(::Tiger, ::Cat) at ... + # => fight(::Lion, ::Cat) at ... + # => ... catch e 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 (generic function with 4 methods) # 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 + # => ERROR: MethodError: fight(::Lion, ::Lion) is ambiguous. Candidates: + # => fight(c::Cat, l::Lion) in Main at ... + # => fight(l::Lion, c::Cat) in Main at ... + # => Possible fix, define + # => fight(::Lion, ::Lion) + # => ... catch e 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 (generic function with 5 methods) +fight(Lion("RAR"), Lion("brown", "rarrr")) # => The lions come to a tie # Under the hood @@ -706,74 +739,112 @@ 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,)) - # .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 - -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 - # +code_native(square_area, (Int32,), syntax = :intel) + # .text + # ; Function square_area { + # ; Location: REPL[116]:1 # Prologue + # push rbp + # mov rbp, rsp + # ; Function *; { + # ; Location: int.jl:54 + # imul ecx, ecx # Square l and store the result in ECX + # ;} + # mov eax, ecx + # pop rbp # Restore old base pointer + # ret # Result will still be in EAX + # nop dword ptr [rax + rax] + # ;} + +code_native(square_area, (Float32,), syntax = :intel) + # .text + # ; Function square_area { + # ; Location: REPL[116]:1 + # push rbp + # mov rbp, rsp + # ; Function *; { + # ; Location: float.jl:398 + # vmulss xmm0, xmm0, xmm0 # Scalar single precision multiply (AVX) + # ;} + # pop rbp + # ret + # nop word ptr [rax + rax] + # ;} + +code_native(square_area, (Float64,), syntax = :intel) + # .text + # ; Function square_area { + # ; Location: REPL[116]:1 + # push rbp + # mov rbp, rsp + # ; Function *; { + # ; Location: float.jl:399 + # vmulsd xmm0, xmm0, xmm0 # Scalar double precision multiply (AVX) + # ;} + # pop rbp + # ret + # nop word ptr [rax + rax] + # ;} + # 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 -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 - # - -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 - # +code_native(circle_area, (Int32,), syntax = :intel) + # .text + # ; Function circle_area { + # ; Location: REPL[121]:1 + # push rbp + # mov rbp, rsp + # ; Function *; { + # ; Location: operators.jl:502 + # ; Function *; { + # ; Location: promotion.jl:314 + # ; Function promote; { + # ; Location: promotion.jl:284 + # ; Function _promote; { + # ; Location: promotion.jl:261 + # ; Function convert; { + # ; Location: number.jl:7 + # ; Function Type; { + # ; Location: float.jl:60 + # vcvtsi2sd xmm0, xmm0, ecx # Load integer (r) from memory + # movabs rax, 497710928 # Load pi + # ;}}}}} + # ; Function *; { + # ; Location: float.jl:399 + # vmulsd xmm1, xmm0, qword ptr [rax] # pi * r + # vmulsd xmm0, xmm1, xmm0 # (pi * r) * r + # ;}} + # pop rbp + # ret + # nop dword ptr [rax] + # ;} + +code_native(circle_area, (Float64,), syntax = :intel) + # .text + # ; Function circle_area { + # ; Location: REPL[121]:1 + # push rbp + # mov rbp, rsp + # movabs rax, 497711048 + # ; Function *; { + # ; Location: operators.jl:502 + # ; Function *; { + # ; Location: promotion.jl:314 + # ; Function *; { + # ; Location: float.jl:399 + # vmulsd xmm1, xmm0, qword ptr [rax] + # ;}}} + # ; Function *; { + # ; Location: float.jl:399 + # vmulsd xmm0, xmm1, xmm0 + # ;} + # pop rbp + # ret + # nop dword ptr [rax + rax] + # ;} ``` ## Further Reading |