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Update to Julia 1.0 (Finish 6/6)

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0u0 2018-08-31 07:55:10 +08:00
parent efd37d9695
commit 207e16a931

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@ -336,7 +336,6 @@ 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])
####################################################
## 3. 控制语句
####################################################
@ -409,81 +408,88 @@ catch e
end
# => caught it ErrorException("help")
####################################################
## 4. 函数
####################################################
# 用关键字 'function' 可创建一个新函数
#function name(arglist)
# body...
#end
# 关键字 'function' 用于定义函数
# function name(arglist)
# body...
# end
function add(x, y)
println("x is $x and y is $y")
# 最后一行语句的值为返回
# 函数会返回最后一行的值
x + y
end
add(5, 6) # => 在 "x is 5 and y is 6" 后会打印 11
add(5, 6)
# => x is 5 and y is 6
# => 11
# 更紧凑的定义函数
f_add(x, y) = x + y # => f_add (generic function with 1 method)
f_add(3, 4) # => 7
# 函数可以将多个值作为元组返回
fn(x, y) = x + y, x - y # => fn (generic function with 1 method)
fn(3, 4) # => (7, -1)
# 还可以定义接收可变长参数的函数
function varargs(args...)
return args
# 关键字 return 可在函数内部任何地方返回
# 使用 return 可以在函数内的任何地方返回
end
# => varargs (generic function with 1 method)
varargs(1,2,3) # => (1,2,3)
# 省略号 ... 称为 splat.
# 省略号 ... 称为 splat
# 刚刚用在了函数定义中
# 还可以用在函数的调用
# Array 或者 Tuple 的内容会变成参数列表
Set([1,2,3]) # => Set{Array{Int64,1}}([1,2,3]) # 获得一个 Array 的 Set
Set([1,2,3]...) # => Set{Int64}(1,2,3) # 相当于 Set(1,2,3)
# 在调用函数时也可以使用它,此时它会把数组或元组解包为参数列表
add([5,6]...) # 等价于 add(5,6)
x = (1,2,3) # => (1,2,3)
Set(x) # => Set{(Int64,Int64,Int64)}((1,2,3)) # 一个 Tuple 的 Set
Set(x...) # => Set{Int64}(2,3,1)
x = (5, 6) # => (5,6)
add(x...) # 等价于 add(5,6)
# 可定义可选参数的函数
function defaults(a,b,x=5,y=6)
# 可定义带可选参数的函数
function defaults(a, b, x=5, y=6)
return "$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"
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
# 还可以定义键值对的参
function keyword_args(;k1=4,name2="hello") # note the ;
return ["k1"=>k1,"name2"=>name2]
# 还可以定义带关键字参数的函
function keyword_args(;k1=4, name2="hello") # 注意分号 ';'
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]
# 可以组合各种类型的参数在同一个函数的参数列表中
# 可以在一个函数中组合各种类型的参数
function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo")
println("normal arg: $normal_arg")
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:
# normal arg: 1
# optional arg: 3
# keyword arg: 4
# => normal arg: 1
# => optional arg: 3
# => keyword arg: 4
# Julia 有一等函数
function create_adder(x)
@ -492,14 +498,16 @@ function create_adder(x)
end
return adder
end
# => create_adder (generic function with 1 method)
# 这是用 "stabby lambda syntax" 创建的匿名函数
(x -> x > 2)(3) # => true
# 这个函数和上面的 create_adder 一模一样
# 这个函数和上面的 create_adder 是等价的
function create_adder(x)
y -> x + y
end
# => create_adder (generic function with 1 method)
# 你也可以给内部函数起个名字
function create_adder(x)
@ -508,18 +516,19 @@ 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
# 内置的高阶函数有
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]
# 还可以使用 list comprehensions 替代 map
[add_10(i) for i=[1, 2, 3]] # => [11, 12, 13]
[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
# 还可以使用 list comprehensions 让 map 更美观
[add_10(i) for i = [1, 2, 3]] # => [11, 12, 13]
[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
####################################################
## 5. 类型
@ -531,248 +540,304 @@ filter(x -> x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
typeof(5) # => Int64
# 类型是一等值
typeof(Int64) # => DataType
typeof(DataType) # => DataType
typeof(Int64) # => DataType
typeof(DataType) # => DataType
# DataType 是代表类型的类型,也代表他自己的类型
# 类型可用作文档化,优化,以及调度
# 并不是静态检查类型
# 类型可用于文档化代码、执行优化以及多重派分(dispatch)
# Julia 并不是静态检查类型
# 用户还可以自定义类型
# 跟其他语言的 records 或 structs 一样
# 用 `type` 关键字定义新的类型
# 就跟其它语言的 records 或 structs 一样
# 用 `struct` 关键字定义新的类型
# type Name
# struct Name
# field::OptionalType
# ...
# end
type Tiger
taillength::Float64
coatcolor # 不带类型标注相当于 `::Any`
struct Tiger
taillength::Float64
coatcolor # 不带类型标注相当于 `::Any`
end
# 构造函数参数是类型的属性
tigger = Tiger(3.5,"orange") # => Tiger(3.5,"orange")
# 默认构造函数参数是类型的属性,按类型定义中的顺序排列
tigger = Tiger(3.5, "orange") # => Tiger(3.5, "orange")
# 用新类型作为构造函数还会创建一个类型
sherekhan = typeof(tigger)(5.6,"fire") # => Tiger(5.6,"fire")
sherekhan = typeof(tigger)(5.6, "fire") # => Tiger(5.6, "fire")
# struct 类似的类型被称为具体类型
# 他们可被实例化但不能有子类型
# 类似 struct 的类型被称为具体类型
# 它们可被实例化,但不能有子类型
# 另一种类型是抽象类型
# abstract Name
abstract Cat # just a name and point in the type hierarchy
# 抽象类型名
abstract type Cat end # 仅仅是指向类型结构层次的一个名称
# 抽象类型不能被实例化,但可以有子类型
# 抽象类型不能被实例化,但可以有子类型
# 例如Number 就是抽象类型
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(Number) # => 2-element Array{Any,1}:
# => Complex
# => Real
subtypes(Cat) # => 0-element Array{Any,1}
# 所有的类型都有父类型; 可以用函数 `super` 得到父类型.
# AbstractString类如其名也是一个抽象类型
subtypes(AbstractString) # => 4-element Array{Any,1}:
# => String
# => SubString
# => SubstitutionString
# => Test.GenericString
# 所有的类型都有父类型。可以用函数 `supertype` 得到父类型
typeof(5) # => Int64
super(Int64) # => Signed
super(Signed) # => Real
super(Real) # => Number
super(Number) # => Any
super(super(Signed)) # => Number
super(Any) # => Any
# 所有这些类型,除了 Int64, 都是抽象类型.
supertype(Int64) # => Signed
supertype(Signed) # => Integer
supertype(Integer) # => Real
supertype(Real) # => Number
supertype(Number) # => Any
supertype(supertype(Signed)) # => Real
supertype(Any) # => Any
# 除了 Int64 外,其余的类型都是抽象类型
typeof("fire") # => String
supertype(String) # => AbstractString
supertype(AbstractString) # => Any
supertype(SubString) # => AbstractString
# <: 是类型集成操作符
type Lion <: Cat # Lion 是 Cat 的子类型
mane_color
roar::String
# <: 是子类型化操作符
struct Lion <: Cat # Lion 是 Cat 的子类型
mane_color
roar::AbstractString
end
# 可以继续为你的类型定义构造函数
# 只需要定义一个同名的函数
# 并调用已有的构造函数设置一个固定参数
Lion(roar::String) = Lion("green",roar)
# 这是一个外部构造函数,因为他再类型定义之外
# 只需要定义一个与类型同名的函数,并调用已有的构造函数得到正确的类型
Lion(roar::AbstractString) = Lion("green", roar) # => Lion
# 这是一个外部构造函数,因为它在类型定义之外
type Panther <: Cat # Panther 也是 Cat 的子类型
eye_color
Panther() = new("green")
# Panthers 只有这个构造函数,没有默认构造函数
struct Panther <: Cat # Panther 也是 Cat 的子类型
eye_color
Panther() = new("green")
# Panthers 只有这个构造函数,没有默认构造函数
end
# 使用内置构造函数,如 Panther可以让你控制
# 如何构造类型的值
# 应该尽可能使用外部构造函数而不是内部构造函数
# 像 Panther 一样使用内置构造函数,让你可以控制如何构建类型的值
# 应该尽量使用外部构造函数,而不是内部构造函数
####################################################
## 6. 多分派
####################################################
# 在Julia中, 所有的具名函数都是类属函数
# 这意味着他们都是有很大小方法组成的
# 每个 Lion 的构造函数都是类属函数 Lion 的方法
# Julia 中所有的函数都是通用函数,或者叫做泛型函数(generic functions)
# 也就是说这些函数都是由许多小方法组合而成的
# Lion 的每一种构造函数都是通用函数 Lion 的一个方法
# 我们来看一个非构造函数的例子
# 首先,让我们定义一个函数 meow
# Lion, Panther, Tiger 的 meow 定义
# Lion, Panther, Tiger 的 meow 定义分别
function meow(animal::Lion)
animal.roar # 使用点符号访问属性
animal.roar # 使用点记号 '.' 访问属性
end
function meow(animal::Panther)
"grrr"
"grrr"
end
function meow(animal::Tiger)
"rawwwr"
"rawwwr"
end
# 试试 meow 函数
meow(tigger) # => "rawwr"
meow(Lion("brown","ROAAR")) # => "ROAAR"
meow(tigger) # => "rawwwr"
meow(Lion("brown", "ROAAR")) # => "ROAAR"
meow(Panther()) # => "grrr"
# 再看看层次结构
issubtype(Tiger,Cat) # => false
issubtype(Lion,Cat) # => true
issubtype(Panther,Cat) # => true
# 回顾类型的层次结构
Tiger <: Cat # => false
Lion <: Cat # => true
Panther <: Cat # => true
# 定义一个接收 Cats 的函数
# 定义一个接收 Cat 类型的函数
function pet_cat(cat::Cat)
println("The cat says $(meow(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
# 在面向对象语言中,通常都是单分派
# 这意味着分派方法是通过第一个参数的类型决定的
# 在Julia中, 所有参数类型都会被考虑到
# 这意味着使用的方法取决于第一个参数的类型
# 而 Julia 中选择方法时会考虑到所有参数的类型
# 让我们定义有多个参数的函数,好看看区别
function fight(t::Tiger,c::Cat)
println("The $(t.coatcolor) tiger wins!")
# 让我们定义一个有更多参数的函数,这样我们就能看出区别
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()) # => The orange tiger wins!
fight(tigger, Lion("ROAR")) # => fight(tigger, Lion("ROAR"))
# 让我们修改一下传入具体为 Lion 类型时的行为
fight(t::Tiger,l::Lion) = println("The $(l.mane_color)-maned lion wins!")
# 让我们修改一下传入 Lion 类型时的行为
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!
# 把 Tiger 去掉
fight(l::Lion,c::Cat) = println("The victorious cat says $(meow(c))")
# 我们不需要一只老虎参与战斗
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")) # => ERROR: no method fight(Panther,Lion)
catch
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)
end
# 在试试让 Cat 在前面
fight(c::Cat,l::Lion) = println("The cat beats the Lion")
# => Warning: New definition
# fight(Cat,Lion) at none:1
# is ambiguous with
# fight(Lion,Cat) at none:2.
# Make sure
# fight(Lion,Lion)
# is defined first.
#fight (generic function with 4 methods)
# 试试把 Cat 放在前面
fight(c::Cat, l::Lion) = println("The cat beats the Lion")
# => fight (generic function with 4 methods)
# 警告说明了无法判断使用哪个 fight 方法
fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr
# 结果在老版本 Julia 中可能会不一样
# 由于无法判断该使用哪个 fight 方法,而产生了错误
try
fight(Lion("RAR"), Lion("brown", "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)
end
# 在不同版本的 Julia 中错误信息可能有所不同
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
# 你还可以看看 llvm 以及生成的汇编代码
# 你还可以看看 llvm 以及生成的汇编代码
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
# 给 square_area 一个整形时发生什么
# 当我们喂给 square_area 一个整数时会发生什么?
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
# .text
# ; Function square_area {
# ; Location: REPL[49]:1
# pushq %rbp
# movq %rsp, %rbp
# ; Function *; {
# ; Location: int.jl:54
# imull %ecx, %ecx
# ;}
# movl %ecx, %eax
# popq %rbp
# retq
# nopl (%rax,%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
# .text
# ; Function square_area {
# ; Location: REPL[49]:1
# pushq %rbp
# movq %rsp, %rbp
# ; Function *; {
# ; Location: float.jl:398
# vmulss %xmm0, %xmm0, %xmm0
# ;}
# popq %rbp
# retq
# nopw (%rax,%rax)
# ;}
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
#
# 注意 只要参数中又浮点类型Julia 就使用浮点指令
# .text
# ; Function square_area {
# ; Location: REPL[49]:1
# pushq %rbp
# movq %rsp, %rbp
# ; Function *; {
# ; Location: float.jl:399
# vmulsd %xmm0, %xmm0, %xmm0
# ;}
# popq %rbp
# retq
# nopw (%rax,%rax)
# ;}
# 注意只要参数中有浮点数Julia 就会使用浮点指令
# 让我们计算一下圆的面积
circle_area(r) = pi * r * r # circle_area (generic function with 1 method)
circle_area(5) # 78.53981633974483
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
#
# .text
# ; Function circle_area {
# ; Location: REPL[53]:1
# pushq %rbp
# movq %rsp, %rbp
# ; 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
# vcvtsi2sdl %ecx, %xmm0, %xmm0
# movabsq $532051920, %rax # imm = 0x1FB677D0
# ;}}}}}
# ; Function *; {
# ; Location: float.jl:399
# vmulsd (%rax), %xmm0, %xmm1
# vmulsd %xmm0, %xmm1, %xmm0
# ;}}
# popq %rbp
# retq
# nopl (%rax)
# ;}
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
#
# .text
# ; Function circle_area {
# ; Location: REPL[53]:1
# pushq %rbp
# movq %rsp, %rbp
# movabsq $532052040, %rax # imm = 0x1FB67848
# ; Function *; {
# ; Location: operators.jl:502
# ; Function *; {
# ; Location: promotion.jl:314
# ; Function *; {
# ; Location: float.jl:399
# vmulsd (%rax), %xmm0, %xmm1
# ;}}}
# ; Function *; {
# ; Location: float.jl:399
# vmulsd %xmm0, %xmm1, %xmm0
# ;}
# popq %rbp
# retq
# nopl (%rax,%rax)
# ;}
```