Method parse

src/common/number/numericString.ts:64–143

(
    input: string,
    targetRadix?: NumericStringRadix,
  )

  // Return parse result and offset of suffix
  public static parse(
    input: string,
    targetRadix?: NumericStringRadix,
  ): { num: NumericString; suffixOffset: number } | undefined {
    const filteredMatchings =
      targetRadix !== undefined
        ? NumericString.matchings.filter((matching) => matching.radix === targetRadix)
        : NumericString.matchings;

    // Find core numeric part of input
    let coreBegin = -1;
    let coreLength = -1;
    let coreRadix = -1;
    let coreSign = false;
    for (const { regex, radix } of filteredMatchings) {
      const match = regex.exec(input);
      if (match != null) {
        // Get the leftmost and largest match
        if (
          coreRadix < 0 ||
          match.index < coreBegin ||
          (match.index === coreBegin && match[0].length > coreLength)
        ) {
          coreBegin = match.index;
          coreLength = match[0].length;
          coreRadix = radix;
          coreSign = match[1] === '-';
        }
      }
    }

    if (coreRadix < 0) {
      return undefined;
    }

    const coreEnd = coreBegin + coreLength;

    const prefix = input.slice(0, coreBegin);
    const core = input.slice(coreBegin, coreEnd);
    const suffix = input.slice(coreEnd, input.length);

    let value = parseInt(core, coreRadix);

    // 0x00ff:  numLength = 4
    // 077:     numLength = 2
    // -0999:   numLength = 3
    // The numLength is only useful for parsing non-decimal. Decimal with
    // leading zero will be trimmed in `toString()`. If value is negative,
    // remove the width of negative sign.
    const numLength = coreLength - NumericString.numPrefix[coreRadix].length - (coreSign ? 1 : 0);

    // According to original vim's behavior, for hex and octal, the leading
    // '-' *should* be captured and preserved but *should not* be regarded as
    // part of number, which means with <C-a>, `-0xf` turns into `-0x10`. So
    // for hex and octal, we make the value absolute and set the negative
    // sign flag.
    let negative = false;
    if (coreRadix !== 10 && coreSign) {