Question

I am trying to implement a recursive loop in LESS 1.3.1. Never you mind what the mix-in is supposed to do (it has something to do with colors) in the end, but do mind why the recursive loop fails.

@iter: 4;

.loop(@index, @n) when (@index <= @n) { // throws "expected expression"?
    .foo@{index} { color: black; }
    .loop(@index + 1, @n);
}

.loop(@index, @n) when (@index > @n) {
    .terminated { color: white; }
}

.loop(1, @iter);

The mix-in .loop is supposed to do 4 iterations and then terminate, doing a .terminated {} or something.

Answer 1

You have your = and > the wrong way round

Less Mixin Guards Documentation

“The full list of comparison operators usable in guards are: > >= = =< <. Additionally, the keyword true is the only truthy value, making these two mixins equivalent:”

.loop(@index, @n) when (@index <= @n)

should be

.loop(@index, @n) when (@index =< @n)