Mixins to convert "em, rem and px" units with stylus

mixins.styl

$basefont = 14px

em(size, parentFontSize = 0)
	if parentFontSize == 0
		font-size round(( size / $basefont )em , 3)
	else 
		font-size round(( size / parentFontSize )em , 3)
rem(size)
	font-size ( size )px
	font-size round(( size / $basefont )rem , 3)
px(size)
	font-size ( size * $basefont )px


// Example usage
// em(12px)
// em(20px, 12px)
// px(2.5em)
// rem(18px)