1894.less

#usage {
    .set(result-1, 1 lt 2, "true", "false");
    .set(result-2, 3 eq 3, "true-only");
    .set(result-3, 4 ne 4, "hidden");

    .set(result-4, iscolor(blue), "true", "false");
    .set(result-5, iscolor(55),   "true", "false");
    .set(result-6, isnumber(red), "hidden");
    .set(result-7, isnumber(77),  "true-only");
    
    // etc.
}

// ............................................................
// implementation:

.set(@property, @condition, @true-value, @false-value: none) {
    .-cond(@condition);
    .true()  {@{property}: @true-value}
    .false() {@{property}: @false-value}
}

.-cond(true)                         {.true}
.-cond(@a, eq, @b) when (@a = @b)    {.true}
.-cond(@a, gt, @b) when (@a > @b)    {.true}
.-cond(@a, ge, @b) when (@a >= @b)   {.true}
.-cond(@a, lt, @b) when (@a < @b)    {.true}
.-cond(@a, le, @b) when (@a <= @b)   {.true}
.-cond(@a, ne, @b) when not(@a = @b) {.true}
.-cond(...) when (default())
    and not(@false-value = none)     {.false}

.-cond(@condition) when (length(@condition) = 3) {
    .-cond(
        extract(@condition, 1),
        extract(@condition, 2),
        extract(@condition, 3)
    );
}