I wrote some helper functions in root less file: @randomFunctions : ~`(function(s){ var round = function(n,c){ c = c|0; return Math.round(n * Math.pow(10,c))/Math.pow(10,c); }; var random = function(s,e){ return Math.random() * (e - s) + s; }; global.r = function(s,e,u){ return round(random(s,e)) + u; }; return 'randomFunctions'; })(this)`; then I could generate random numbers using these functions: .r{ opacity : ~`r(0,1)`; } outputs .rr{ opacity : 0.3; } but in a mixin: .r(@i){ .r@{i} { opacity : ~`r(0,1)`; } } .r(1); compiler tells me 'Can not found r function in [object Object]' so I guess the javascript evalution context inside a mixin is different with the context in root. Will this be fixed in next version? or just add another way to pass a function inside mixin so I can release the power of javascript in less file?