The CSS Preprocessor adds the capability to write complex expressions and functions to use in your CSS files.
One of the functions you can use is a system function named if. It is used to select one of two expressions as shown here:
if($color = white, 33px, 145px)
This says if $color represents the color white, then use 33px, otherwise use 145px.
This works great in all cases where the true and false expressions are both calculable. If one of the expressions is to generate an error, then the if() function cannot be used. In this case, you want to use the ?: operator instead.
In the ...