arithmetic-operations-for/naturals-big-endian

/**
 * Converts an input character representation to a limb.
 *
 * @param {string} x input character
 *
 * @return {number} output limb
 */
export default function _int(x) {
    // eslint-disable-next-line unicorn/prefer-code-point
    if (x >= '0' && x <= '9') return x.charCodeAt(0) - 48;
    // eslint-disable-next-line unicorn/prefer-code-point
    if (x >= 'A' && x <= 'Z') return x.charCodeAt(0) - 55;
    // eslint-disable-next-line unicorn/prefer-code-point
    if (x >= 'a' && x <= 'z') return x.charCodeAt(0) - 87;

    throw new Error('invalid literal for _int: ' + x);
}