Define LESS variable from string - less

Question

I'm trying to write a mixin that returns a variable for converting px to em. I've toyed with a few things, but ultimately i'd like to call a mixin and get a return value similar to SASS's functions. Based on on return values here: http://www.lesscss.org/#-return-values, I can only define a variable once as a return value. Example:
Mixin
.px-to-emz( #size, #base: #font-size-base ){
#em: round( unit( (#size / #base), ~"em" ), 3 );
}
Call it:
.foo {
font-size: #em;
.px-to-emz(10, 16px);
height: #em;
.px-to-emz(200, 16px);
}
Fine, if you want to only return one variable, but if i want to return multiple variables I need to define new variable names. Here's what i'd ideally like to do
Mixin:
.px-to-ems( #size, #var: 'em', #base: #font-size-base ){
~'#{var}': round( unit( (#size / #base), ~"em" ), 3 );
}
Call it:
.foo {
font-size: #font-size;
.px-to-ems(10, 'font-size', 16px);
height: #height;
.px-to-ems(200, 'height', 16px);
}

Answer 1

#1
So far the best known solution for this problem is to put each mixin call into its own scope:
.px-to-ems(#size, #base: #font-size-base) {
#-: round(unit((#size / #base), em), 3);
}
.foo {
.-() {font-size: #-; .px-to-ems( 10, 16px)}
.-() {height: #-; .px-to-ems(200, 16px)}
.-;
}
Replace #- and .- with whatever identifiers you find suitable.
#2
The other way around is to use recently added (Less 1.6.x) property interpolation feature:
.px-to-ems(#property, #size, #base: #font-size-base) {
#{property}: round(unit((#size / #base), em), 3);
}
.foo {
.px-to-ems(font-size, 10, 16px);
.px-to-ems(height, 200, 16px);
}
It's more clean than #1 if you simply need to assign the "function" result to a property.