GLSL vector Swizzling in Julia

swizzle.jl

macro swizzle(vec, components)
    function index(component)
        (component == 'x' || component == 'r') && return 1
        (component == 'y' || component == 'g') && return 2
        (component == 'z' || component == 'b') && return 3
        (component == 'w' || component == 'a') && return 4
        error("swizzling components must be one of x, y, z, w")
    end
 
    accesses = [Expr(:ref, :vec, index(component)) for component in string(components)]
    
    quote
        let vec = $(esc(vec)), type = $Base.eltype(vec)
            $(Expr(:ref, :type, accesses...))
        end
    end
end

myvec = [1, 2, 3, 4]
println(@swizzle myvec xyxzr) # [1, 2, 1, 3, 1]