逻辑运算符 #

!true
!false
true && true
true && false
false && true
false && false
true || true
true || false
false || true
false || false

false && println("This won't print")
true && println("This will print")

true || println("This won't print")
false || println("This will print")

x = 5
x > 0 && println("Positive")
x < 0 || println("Non-negative")

name = nothing
actual_name = name || "Anonymous"

~0b1010
0b1010 & 0b1100
0b1010 | 0b1100
0b1010 ⊻ 0b1100
0b1000 >>> 2
0b1000 >> 2
0b0010 << 2

x = 0b1010
x & 0b1000
x | 0b0100
x ⊻ 0b1111

any([false, false, true])
any([false, false, false])
all([true, true, true])
all([true, false, true])

arr = [1, 2, 3, 4, 5]
any(x -> x > 3, arr)
all(x -> x > 0, arr)

arr = [1, 2, 3, 4, 5]
count(x -> x > 3, arr)
count(x -> x % 2 == 0, arr)

condition ? value_if_true : value_if_false

x = 5
x > 0 ? "Positive" : "Non-positive"

x = 0
x > 0 ? "Positive" : x < 0 ? "Negative" : "Zero"

x = 5

result = x > 0 ? "Positive" : "Non-positive"

result = if x > 0
    "Positive"
else
    "Non-positive"
end

function safe_divide(a, b)
    b != 0 && return a / b
    return nothing
end

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

function validate_age(age)
    age >= 0 || error("Age cannot be negative")
    age <= 150 || error("Age seems unrealistic")
    return true
end

validate_age(25)
validate_age(-1)

function greet(name)
    actual_name = name === nothing ? "Guest" : name
    println("Hello, $actual_name!")
end

greet("Julia")
greet(nothing)

const READ = 0b100
const WRITE = 0b010
const EXECUTE = 0b001

function has_permission(permissions, flag)
    (permissions & flag) != 0
end

perms = READ | WRITE
has_permission(perms, READ)
has_permission(perms, EXECUTE)