Can you set a variable inside a mixin in LESS CSS? - less

Question

I understand LESS doesn't have if/else structure and instead relies on guarded mixin statements. It doesn't appear to be able to set a LESS CSS variable inside of a mixin though.
Anyone have an idea of how I could implement something to the effect of.
if( ispercentage( #height ) {
#height: "1024px";
}
// Calculations dependent on #height
#textAreaHeight = 0.5 * #height;
#buttonHeight = 0.2 * #height;
I've looked at several other stackoverflow questions including:
LESS CSS - Setting variable within mixin

Answer 1

Yes, it can be done. There was one bug that needed to be worked around.
Example LESS Code
//Set up guarded mixins
.setHeight(#h) when (ispercentage(#h)) {
#height: 1024px;
}
.setHeight(#h) when not (ispercentage(#h)) {
#height: #h;
}
//set up main height
#mainHeight: 50%;
body { height: #mainHeight;}
//call it by itself to make global
//.setHeight(#mainHeight); <-this failed (appears to be a bug)
.setHeight(50%); // <-this worked
.subsection { height: #height; /* just to show it is setting it */}
//use it for other globals
#textAreaHeight: 0.5 * #height;
#buttonHeight: 0.2 * #height;
textarea { height: #textAreaHeight}
button { height: #buttonHeight}
//override it locally
body.fixedHeight {
.setHeight(300px);
#textAreaHeight: 0.333 * #height;
height: #height;
textarea { height: #textAreaHeight}
}
Example CSS Output
body {
height: 50%;
}
.subsection {
height: 1024px; /* just to show it is setting it */
}
textarea {
height: 512px;
}
button {
height: 204.8px;
}
body.fixedHeight {
height: 300px;
}
body.fixedHeight textarea {
height: 99.9px;
}

Answer 2

You can create a mixin that is "guarded" by the type, e.g.
.doHeightSet(#height) when ispercentage(#height) {
.doheightSet(1024px)
}
.doHeightSet(#height) when not ispercentage(#height) {
// Calculations dependent on #height
#textAreaHeight: 0.5 * #height;
#buttonHeight: 0.2 * #height;
/* use variables here */
}
Sorry, I don't have time to try this out, so I may have made a syntax mistake.
edit corrected syntax.