// Returns base to the exponent power.
// @param {Number} $base The base number
// @param {Number} $exp The exponent to which to raise base
// @return {Number}
// @example
//     pow(4, 2)   // 16
//     pow(4, -2)  // 0.0625
//     pow(4, 0.2) // 1.31951
@function pow ($base, $exp) {
    @if $exp == floor($exp) {
        $r: 1;
        $s: 0;
        @if $exp < 0 {
            $exp: $exp * -1;
            $s: 1;
        }
        @while $exp > 0 {
            @if $exp % 2 == 1 {
                $r: $r * $base;
            }
            $exp: floor($exp * 0.5);
            $base: $base * $base;
        }
        @return if($s != 0, 1 / $r, $r);
    } @else {
        @return exp(log($base) * $exp);
    }
}