@function __parse-int($string, $radix: null, $guard: null) {
    @if ($guard and __is-iteratee-call($string, $radix, $guard)) {
        $radix: 10;
    }

    @if __is-falsey($string) {
        @return 0;
    }

    $string: to-upper-case(__trim($string));

    @if __is-falsey($radix) {
        $radix: if(__starts-with($string, ('0X', '#')), 16, 10);
    }

    $result: 0;
    $multiplier: if(__starts-with($string, '-'), -1, 1);
    $prefix: if(__starts-with($string, ('-', '+', '#')), 1, if(__starts-with($string, ('0X')), 2, 0));
    $char-min: __get-char-code(0);
    $char-max: $char-min + 9;
    $char-alpha-min: __get-char-code('A'); // 10
    $char-alpha-max: __get-char-code('Z');
    $char-codes: __map($string, '__get-char-code');
    $index: $prefix + 1;
    $break: false;

    @while $index <= length($char-codes) and not $break {
        $char-code: nth($char-codes, $index);

        @if $char-code >= $char-min and $char-code <= $char-max {
            $result: ($radix * $result) + ($char-code - $char-min);
        } @else if $char-code >= $char-alpha-min and $char-code < $char-alpha-max {
            $result: ($radix * $result) + ($char-code - $char-alpha-min + 10);
        } @else {
            $break: true;
        }

        $index: $index + 1;
    }

    @return $multiplier * $result;
}

/// Parses a string argument and returns an integer of the specified radix
/// (the base in mathematical numerical systems).
/// 
/// Similar to native JavaScript [parseInt() function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseInt).
/// 
/// @access public
/// @group Number
/// @param {String} $string The value to parse. If string is not a string,
///  then it is converted to one. Leading whitespace in the string is ignored.
/// @param {Number} $radix An integer between 2 and 36 that represents the radix
///  (the base in mathematical numeral systems) of the above mentioned string. 
/// @returns {Number} Returns the string converted to an integer, or `null`.
/// @example scss
/// 
/// $foo: _parse-int('10');
/// // => 10
/// 
/// $foo: _parse-int('#000020');
/// // => 32
/// 
/// $foo: _parse-int('    123');
/// // => 123

@function _parse-int($args...) {
    @return call(get-function('__parse-int'), $args...);
}