Default parameter values should be able to refer to previous parameters

[jeffpatzer]

@mixin font-size($font-size,$lines:ceil($font-size / $base-line-height)){
    font-size:$font-size;
    line-height:rhythm($lines,$font-size);
}

Notice the use of $font-size in the arg list. This will fail, but works in normal scss.

[akhleung]

This is a semantically weird thing for Sass to allow, but I'll duplicate it if it's standard and existing code depends on it.

[chriseppstein]

Yes, any parameter can have a default value that depends on the value of the previous arguments. Python does this too and it's really quite nice.

[akhleung]

Fixed!