类型注解 #

x::Int = 10
y::Float64 = 3.14
name::String = "Julia"

x = 10
x::Int
x::Float64

x = 10.5
x::Int

global x::Int = 10

function modify_x()
    global x += 1
end

x
modify_x()
x

function process()
    x::Int = 10
    x += 1
    return x
end

process()

x::Int = 10
x = "hello"

function add(a::Int, b::Int)
    a + b
end

add(1, 2)
add(1.0, 2.0)

function process(x::Union{Int, Float64})
    x * 2
end

process(10)
process(10.5)
process("hello")

function first(arr::Vector{T}) where {T}
    arr[1]
end

first([1, 2, 3])
first(["a", "b", "c"])

function add(a::Int, b::Int)::Int
    a + b
end

function create_point(x, y)::Tuple{Float64, Float64}
    (Float64(x), Float64(y))
end

create_point(1, 2)

function safe_divide(a, b)::Union{Float64, Nothing}
    b == 0 ? nothing : a / b
end

safe_divide(10, 2)
safe_divide(10, 0)

struct Point
    x::Float64
    y::Float64
end

p = Point(1.0, 2.0)
p.x

struct Container{T}
    value::T
end

Container(10)
Container("hello")

function calculate_area(width::Float64, height::Float64)::Float64
    width * height
end

function process(x::Int)
    x * 2
end

process(10)
process(10.0)

function sum_array(arr::Vector{Int})
    total = 0
    for x in arr
        total += x
    end
    total
end

function divide(a::Real, b::Real)::Float64
    b == 0 && error("Division by zero")
    a / b
end

divide(10, 2)
divide(10.0, 2.0)
divide(10, 0)

function to_string(x)::String
    string(x)
end

to_string(10)
to_string(3.14)
to_string([1, 2, 3])

function type_check(x, expected_type::Type)
    if x isa expected_type
        println("✓ $x is $expected_type")
        return true
    else
        println("✗ $x is $(typeof(x)), expected $expected_type")
        return false
    end
end

type_check(1, Int)
type_check(1.0, Int)
type_check("hello", String)