0.15e+0_2    // == 15.0

0x1p-2       // == 0.25
0x2.p10      // == 2048.0
0x1.Fp+0     // == 1.9375
0X.8p-0      // == 0.5
0X_1FFFP-16  // == 0.1249847412109375
0x15e-2      // == 0x15e - 2 (integer subtraction)

0x.p1        // invalid: mantissa has no digits
1p-2         // invalid: p exponent requires hexadecimal mantissa
0x1.5e-2     // invalid: hexadecimal mantissa requires p exponent

a pair of values\n   * as `String` divided by a comma or one (or more) white spaces.<br />\n   * The latter is a deprecated method because it leads to confusion and will be\n   * removed in v2.<br />\n   * Additionally, it accepts additions and subtractions between different units.\n   * Note that multiplications and divisions aren't supported.\n   *\n   * Valid examples are:\n   * ```\n   * 10\n   * '10%'\n   * '10, 10'\n   * '10%, 10'\n   * '10 + 10%'\n   * '10 - 5vh + 3%'\n   * '-10px + 5vh, 5px...