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Julia 快速入门

Julia 快速入门

作者: 朱小虎XiaohuZhu | 来源:发表于2018-12-30 21:58 被阅读79次

    作为一个编程语言爱好者,对新出炉的语言总是心里痒痒的,今天带你走入 Julia 的世界。原文链接:https://learnxinyminutes.com/docs/julia/

    本文基于 Julia 1.0.0。代码

    # Single line comments start with a hash (pound) symbol.
    #= Multiline comments can be written
       by putting '#=' before the text  and '=#'
       after the text. They can also be nested.
    =#
    
    ####################################################
    ## 1. Primitive Datatypes and Operators
    ####################################################
    
    # Everything in Julia is an expression.
    
    # There are several basic types of numbers.
    typeof(3)       # => Int64
    typeof(3.2)     # => Float64
    typeof(2 + 1im) # => Complex{Int64}
    typeof(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
    10 / 2     # => 5.0  # 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
    
    # Use the bitstring function to see the binary representation of a number.
    bitstring(12345)
    # => "0000000000000000000000000000000000000000000000000011000000111001"
    bitstring(12345.0)
    # => "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
    # Comparisons can be chained
    1 < 2 < 3  # => true
    2 < 3 < 2  # => false
    
    # Strings are created with "
    "This is a string."
    
    # Character literals are written with '
    'a'
    
    # Strings are UTF8 encoded. Only if they contain only ASCII characters can
    # they be safely indexed.
    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:
    "2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
    # You can put any Julia expression inside the parentheses.
    
    # Another way to format strings is the printf macro from the stdlib Printf.
    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!") # => 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
    ####################################################
    
    # You don't declare variables before assigning to them.
    someVar = 5  # => 5
    someVar  # => 5
    
    # Accessing a previously unassigned variable is an error
    try
        someOtherVar  # => ERROR: UndefVarError: someOtherVar not defined
    catch e
        println(e)
    end
    
    # 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 certain unicode characters
    ☃ = 8  # => 8
    # These are especially handy for mathematical notation
    2 * π # => 6.283185307179586
    
    # A note on naming conventions in Julia:
    #
    # * 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.
    #
    # * Names of functions and macros are in lower case, without underscores.
    #
    # * Functions that modify their inputs have names that end in !. These
    #   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 Array{Int64,1}
    
    # 1-dimensional array literals can be written with comma-separated values.
    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[1]    # => 4
    b[end]  # => 6
    
    # 2-dimensional arrays use space-separated values and semicolon-separated rows.
    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 Array{Int8,1}: [4, 5, 6]
    
    # Add stuff to the end of a list with push! and append!
    # By convention, the exclamation mark '!'' is appended to names of functions
    # that modify their arguments
    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
    b # => [4,5]
    
    # Let's put it back
    push!(b, 6)  # => [4,5,6]
    b # => [4,5,6]
    
    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
    
    # we also have popfirst! and pushfirst!
    popfirst!(a)  # => 1 
    a # => [2,4,3,4,5,6]
    pushfirst!(a, 7)  # => [7,2,4,3,4,5,6]
    a # => [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 Array{Int64,1}: [5,4,6]
    sort(arr)   # => [4,5,6]
    arr         # => [5,4,6]
    sort!(arr)  # => [4,5,6]
    arr         # => [4,5,6]
    
    # Looking out of bounds is a BoundsError
    try
        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
    
    # Errors list the line and file they came from, even if it's in the standard
    # library. You can look in the folder share/julia inside the julia folder to
    # find these files.
    
    # You can initialize arrays from ranges
    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]
    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 # => [3,5]
    
    # Concatenate lists with append!
    b = [1,2,3]
    append!(a, b) # => [1, 2, 3, 4, 5, 1, 2, 3]
    a # => [1, 2, 3, 4, 5, 1, 2, 3]
    
    # Check for existence in a list with in
    in(1, a)  # => true
    
    # Examine the length with length
    length(a)  # => 8
    
    # Tuples are immutable.
    tup = (1, 2, 3)  # => (1,2,3)
    typeof(tup) # => Tuple{Int64,Int64,Int64}
    tup[1] # => 1
    try
        tup[1] = 3  
        # => ERROR: MethodError: no method matching 
        # setindex!(::Tuple{Int64,Int64,Int64}, ::Int64, ::Int64)
    catch e
        println(e)
    end
    
    # Many array functions also work on tuples
    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 # => 1
    b # => 2
    c # => 3
    
    # Tuples are created even if you leave out the parentheses
    d, e, f = 4, 5, 6  # => (4,5,6)
    d # => 4
    e # => 5
    f # => 6
    
    # A 1-element tuple is distinct from the value it contains
    (1,) == 1 # => false
    (1) == 1  # => true
    
    # Look how easy it is to swap two values
    e, d = d, e  # => (5,4) 
    d # => 5
    e # => 4
    
    # Dictionaries store mappings
    emptyDict = Dict()  # => Dict{Any,Any} with 0 entries
    
    # You can create a dictionary using a literal
    filledDict = Dict("one" => 1, "two" => 2, "three" => 3)
    # => Dict{String,Int64} with 3 entries:
    # =>  "two" => 2, "one" => 1, "three" => 3
    
    # Look up values with []
    filledDict["one"]  # => 1
    
    # Get all keys
    keys(filledDict)
    # => Base.KeySet for a Dict{String,Int64} with 3 entries. Keys:
    # =>  "two", "one", "three"
    # Note - dictionary keys are not sorted or in the order you inserted them.
    
    # Get all values
    values(filledDict)
    # => 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
    in(("one" => 1), filledDict)  # => true
    in(("two" => 3), filledDict)  # => false
    haskey(filledDict, "one")     # => true
    haskey(filledDict, 1)         # => false
    
    # Trying to look up a non-existent key will raise an error
    try
        filledDict["four"]  # => ERROR: KeyError: key "four" not found
    catch e
        println(e)
    end
    
    # Use the get method to avoid that error by providing a default value
    # get(dictionary, key, defaultValue)
    get(filledDict, "one", 4)   # => 1
    get(filledDict, "four", 4)  # => 4
    
    # Use Sets to represent collections of unordered, unique values
    emptySet = Set()  # => Set(Any[])
    # Initialize a set with values
    filledSet = Set([1, 2, 2, 3, 4])  # => Set([4, 2, 3, 1])
    
    # Add more values to a set
    push!(filledSet, 5)  # => Set([4, 2, 3, 5, 1])
    
    # Check if the values are in the set
    in(2, filledSet)   # => true
    in(10, filledSet)  # => false
    
    # There are functions for set intersection, union, and difference.
    otherSet = Set([3, 4, 5, 6])         # => Set([4, 3, 5, 6])
    intersect(filledSet, otherSet)      # => Set([4, 3, 5])
    union(filledSet, otherSet)          # => Set([4, 2, 3, 5, 6, 1])
    setdiff(Set([1,2,3,4]), Set([2,3,5])) # => Set([4, 1])
    
    ####################################################
    ## 3. Control Flow
    ####################################################
    
    # Let's make a variable
    someVar = 5
    
    # Here is an if statement. Indentation is not meaningful in Julia.
    if someVar > 10
        println("someVar is totally bigger than 10.")
    elseif someVar < 10    # This elseif clause is optional.
        println("someVar is smaller than 10.")
    else                    # The else clause is optional too.
        println("someVar is indeed 10.")
    end
    # => prints "some var is smaller than 10"
    
    # For loops iterate over iterables.
    # 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
    end
    # => dog is a mammal
    # => cat is a mammal
    # => mouse is a mammal
    
    # You can use 'in' instead of '='.
    for animal in ["dog", "cat", "mouse"]
        println("$animal is a mammal")
    end
    # => dog is a mammal
    # => cat is a mammal
    # => mouse is a mammal
    
    for pair in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
        from, to = pair
        println("$from is a $to")
    end
    # => 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
    # => mouse is a mammal
    # => cat is a mammal
    # => dog is a mammal
    
    # While loops loop while a condition is true
    let x = 0
        while x < 4
            println(x)
            x += 1  # Shorthand for x = x + 1
        end
    end
    # => 0
    # => 1
    # => 2
    # => 3
    
    # Handle exceptions with a try/catch block
    try
        error("help")
    catch e
        println("caught it $e")
    end
    # => caught it ErrorException("help")
    
    ####################################################
    ## 4. Functions
    ####################################################
    
    # The keyword 'function' creates new functions
    # function name(arglist)
    #   body...
    # end
    function add(x, y)
        println("x is $x and y is $y")
    
        # Functions return the value of their last statement
        x + y
    end
    
    add(5, 6)
    # => x is 5 and y is 6
    # => 11
    
    # Compact assignment of functions
    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 (generic function with 1 method)
    fn(3, 4)  # => (7, -1)
    
    # You can define functions that take a variable number of
    # positional arguments
    function varargs(args...)
        return args
        # use the keyword return to return anywhere in the function
    end
    # => varargs (generic function with 1 method)
    
    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)
    
    x = (5, 6)  # => (5,6)
    add(x...)  # this is equivalent to add(5,6)
    
    
    # You can define functions with optional positional arguments
    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: MethodError: no method matching defaults(::Char)
        defaults()  # => ERROR: MethodError: no method matching defaults()
    catch e
        println(e)
    end
    
    # You can define functions that take keyword arguments
    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")     # => ["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(normalArg, optionalPositionalArg=2; keywordArg="foo")
        println("normal arg: $normalArg")
        println("optional arg: $optionalPositionalArg")
        println("keyword arg: $keywordArg")
    end
    # => all_the_args (generic function with 2 methods)
    
    all_the_args(1, 3, keywordArg=4)
    # => normal arg: 1
    # => optional arg: 3
    # => keyword arg: 4
    
    # Julia has first class functions
    function create_adder(x)
        adder = function (y)
            return x + y
        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
    
    # This function is identical to create_adder implementation above.
    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)
        function adder(y)
            x + y
        end
        adder
    end
    # => create_adder (generic function with 1 method)
    
    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
    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
    [add_10(i) for i = [1, 2, 3]]   # => [11, 12, 13]
    [add_10(i) for i in [1, 2, 3]]  # => [11, 12, 13]
    [x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7]
    
    ####################################################
    ## 5. Types
    ####################################################
    
    # 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
    
    # Types are first-class values
    typeof(Int64)     # => DataType
    typeof(DataType)  # => DataType
    # DataType is the type that represents types, including itself.
    
    # Types are used for documentation, optimizations, and dispatch.
    # They are not statically checked.
    
    # Users can define types
    # They are like records or structs in other languages.
    # New types are defined using the `struct` keyword.
    
    # struct Name
    #   field::OptionalType
    #   ...
    # end
    struct Tiger
        taillength::Float64
        coatcolor  # not including a type annotation is the same as `::Any`
    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")
    
    # The type doubles as the constructor function for values of that type
    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.
    # The other kind of types is abstract types.
    
    # abstract Name
    abstract type Cat end  # 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)  # => 2-element Array{Any,1}:
                      # =>  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
    
    # 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
    # All of these type, except for Int64, are abstract.
    typeof("fire")      # => String
    supertype(String)   # => AbstractString
    # Likewise here with String
    supertype(SubString)  # => AbstractString
    
    # <: is the subtyping operator
    struct Lion <: Cat  # Lion is a subtype of Cat
        maneColor
        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::AbstractString) = Lion("green", roar)
    # This is an outer constructor because it's outside the type definition
    
    struct Panther <: Cat  # Panther is also a subtype of Cat
        eyeColor
        Panther() = new("green")
        # Panthers will only have this constructor, and no default constructor.
    end
    # Using inner constructors, like Panther does, gives you control
    # over how values of the type can be created.
    # When possible, you should use outer constructors rather than inner ones.
    
    ####################################################
    ## 6. Multiple-Dispatch
    ####################################################
    
    # In Julia, all named functions are generic functions
    # This means that they are built up from many small methods
    # Each constructor for Lion is a method of the generic function Lion.
    
    # For a non-constructor example, let's make a function meow:
    
    # Definitions for Lion, Panther, Tiger
    function meow(animal::Lion)
        animal.roar  # access type properties using dot notation
    end
    
    function meow(animal::Panther)
        "grrr"
    end
    
    function meow(animal::Tiger)
        "rawwwr"
    end
    
    # Testing the meow function
    meow(tigger)  # => "rawwwr"
    meow(Lion("brown", "ROAAR"))  # => "ROAAR"
    meow(Panther()) # => "grrr"
    
    # Review the local type hierarchy
    Tiger   <: Cat  # => false
    Lion    <: Cat  # => true
    Panther <: Cat  # => true
    
    # Defining a function that takes Cats
    function pet_cat(cat::Cat)
        println("The cat says $(meow(cat))")
    end
    # => pet_cat (generic function with 1 method)
    
    pet_cat(Lion("42")) # => The cat says 42
    try
        pet_cat(tigger) # => ERROR: MethodError: no method matching pet_cat(::Tiger)
    catch e
        println(e)
    end
    
    # In OO languages, single dispatch is common;
    # this means that the method is picked based on the type of the first argument.
    # In Julia, all of the argument types contribute to selecting the best method.
    
    # Let's define a function with more arguments, so we can see the difference
    function fight(t::Tiger, c::Cat)
        println("The $(t.coatcolor) tiger wins!")
    end
    # => fight (generic function with 1 method)
    
    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.maneColor)-maned lion wins!")
    # => fight (generic function with 2 methods)
    
    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())  # => The victorious cat says grrr
    try
        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
    
    # 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"))
        # => 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
    # The result may be different in other versions of Julia
    
    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
    # You can take a look at the llvm  and the assembly code generated.
    
    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,), 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,), 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]
        # ;}
    

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