示例#1
0
  @Override
  public Success<Expression> parse(String s, int p) {
    // Parse a string of digits before and after the decimal point.
    Success<String> resA = parseDigits(s, p);
    p = resA.rem;
    if (s.charAt(p++) != '.') return null;
    Success<String> resB = parseDigits(s, p);
    p = resB.rem;

    // Put them together.
    String a = resA.value, b = resB.value;
    if (a.isEmpty() && b.isEmpty()) return null;
    StringBuilder sb = new StringBuilder();
    sb.append(a).append('.').append(b);

    // Parse the exponent.
    if (Character.isLowerCase(s.charAt(p))) {
      sb.append(s.charAt(p++));
      if (s.charAt(p) == '-') {
        ++p;
        sb.append('-');
      }
      Success<String> resExp = parseDigits(s, p);
      if (resExp.value.isEmpty()) return null;
      sb.append(resExp.value);
    }

    Expression Success = new LiteralDouble(Double.parseDouble(sb.toString()));
    return new Success<Expression>(Success, p);
  }
示例#2
0
 private static Success<String> parseDigits(String s, int p) {
   StringBuilder sb = new StringBuilder();
   while (Character.isDigit(s.charAt(p))) sb.append(s.charAt(p++));
   return new Success<String>(sb.toString(), p);
 }