ActivePatterns.jl

using MLStyle


@active Re{r :: Regex}(x) begin
    match(r, x)
end


match_numbers = @λ begin
    Re{r"\G\d+"}(_) -> true
    _ -> false
end

@assert match_numbers("12345  ")
@assert !match_numbers("   12345")

struct RGB
    R :: Int
    G :: Int
    B :: Int
end

red = RGB(220, 20, 60)

green = RGB(0, 150, 50)


@active Red(x) begin
    @match (x.R, x.G, x.B) begin
        (118:138, 0:10, 0:10) => :maroon
        (129:149, 0:10, 0:10) => :dark_red
        (210:230, 10:30, 50:70) => :crimson
        (155:175, 32:52, 32:52) => :brown
        (100:255, 0:110, 0:110) => :unknown
        _ => nothing
    end
end

@active Green(x) begin
    @match (x.R, x.G, x.B) begin
        (0:10, 90:110, 0:10) => :dark_green
        (0:10, 118:138, 0:10) => :green
        (24:44, 129:149, 24:44) => :forest_green
        (0:100, 100:255, 0:100) => :unknown
        _ => nothing
    end
end

macro f(x) println(macroexpand(Main, x)) end
@assert @match red begin
        Red(x) => (println(x); true)
        x => (show(x); false)
end

@assert @match green begin
    Green(x) => (println(x); true)
    _ => false
end