比较运算符 #

1 == 1
1 == 2
1 != 2
1 ≠ 2
1 < 2
2 > 1
1 <= 1
1 ≤ 1
1 >= 1
1 ≥ 1

1 < 2 < 3
1 < 2 > 1
1 < 3 == 3
1 < 2 < 3 < 4

x = 5
0 < x < 10
-10 < x < 0

x = 5
1 <= x <= 10
x < 0 || x > 10

NaN == NaN
NaN != NaN
NaN === NaN
isequal(NaN, NaN)
isnan(NaN)

missing == missing
missing === missing
ismissing(missing)
missing === nothing

nothing == nothing
nothing === nothing
isnothing(nothing)

isequal(NaN, NaN)
NaN == NaN
isequal(missing, missing)
missing == missing
isequal(0.0, -0.0)
0.0 == -0.0

1 isa Int
1.0 isa Int
1.0 isa Float64
"hello" isa String
[1, 2, 3] isa Vector

typeof(1) == Int
typeof(1.0) == Float64
typeof(1) <: Integer
typeof(1.0) <: Number

Int <: Integer
Int <: Number
Int <: Real
Float64 <: AbstractFloat
Float64 <: Real

[1, 2, 3] == [1, 2, 3]
[1, 2, 3] == [3, 2, 1]
[1, 2, 3] === [1, 2, 3]

Dict(:a => 1) == Dict(:a => 1)
Dict(:a => 1) == Dict(:a => 2)

Set([1, 2, 3]) == Set([3, 2, 1])
issetequal([1, 2, 3], [3, 2, 1])

"hello" == "hello"
"hello" == "Hello"
"hello" === "hello"

"abc" < "abd"
"abc" < "abcd"
"abc" < "ABC"

lowercase("Hello") == lowercase("hello")
casecmp("Hello", "hello")

0.1 + 0.2 == 0.3
isapprox(0.1 + 0.2, 0.3)
isapprox(0.1 + 0.2, 0.3, atol=1e-10)

0.1 + 0.2 ≈ 0.3
0.1 + 0.2 ≈ 0.3

isapprox(1.0, 1.01, rtol=0.01)
isapprox(1.0, 1.01, atol=0.01)

function in_range(x, lower, upper)
    lower <= x <= upper
end

in_range(5, 1, 10)
in_range(0, 1, 10)

function check_type(x)
    if x isa Int
        "Integer"
    elseif x isa Float64
        "Float"
    elseif x isa String
        "String"
    else
        "Other: $(typeof(x))"
    end
end

check_type(1)
check_type(1.0)
check_type("hello")

function safe_compare(a, b)
    if ismissing(a) || ismissing(b)
        return missing
    elseif isnan(a) || isnan(b)
        return false
    else
        return a == b
    end
end

safe_compare(1, 1)
safe_compare(1, missing)
safe_compare(NaN, NaN)