Whatever.jl

module What
export Whatever, what

struct Whatever{NumArgs, F <: Function}
    f::F
    Whatever{N}(f::F) where {N, F <: Function} = new{N, F}(f)
end

const what = Whatever{1}(identity)

(w::Whatever{N})(args::Vararg{Any, N}) where N = w.f(args...)

for op in [:+, :-, :*, :/, :div, :^, :(==), :>, :<, :>=, :<=, :!=]
    @eval begin
        import Base.$op

        $op(w::Whatever{N}, x) where N =
             Whatever{N}((args...) -> $op(w(args...), x))

        $op(x, w::Whatever{N}) where N =
            Whatever{N}((args...) -> $op(x, w(args...)))

        $op(w1::Whatever{N1}, w2::Whatever{N2}) where {N1, N2} =
            Whatever{N1 + N2}((args...) -> $op(
                w1(args[1:N1]...),
                w2(args[N1+1:end]...),
            ))
    end
end

end