A mixin for Mike Riethmuller fluid typography

mixin-fluid-typography.scss

@mixin fluid-type($min-font-size, $max-font-size, $min-vw: 480px, $max-vw: 1200px) {
    $u1: unit($min-vw);
    $u2: unit($max-vw);
    $u3: unit($min-font-size);
    $u4: unit($max-font-size);
  
    @if $u1 == $u2 and $u1 == $u3 and $u1 == $u4 {
        font-size: $min-font-size;

        @if $min-vw != $max-vw {
            @media only screen and (min-width: $min-vw) {
                font-size: calc(#{$min-font-size} + #{strip-unit($max-font-size - $min-font-size)} * ((100vw - #{$min-vw}) / #{strip-unit($max-vw - $min-vw)}));
            }
        }

        @media only screen and (min-width: $max-vw) {
            font-size: $max-font-size;
        }
    }
    @else {
         @error"Detected mixed units. Please use the same units for all parameters.";
    }
}

@function strip-unit($number) {
    @return $number / ($number * 0 + 1);
}