parse static method

DD parse(String str)

Converts a string representation of a real number into a DoubleDouble value. The format accepted is similar to the standard Java real number syntax. It is defined by the following regular expression:

[+|-] {digit} [ . {digit} ] [ ( e | E ) [+|-] {digit}+

@param str the string to parse @return the value of the parsed number @throws NumberFormatException if str is not a valid representation of a number

Implementation

static DD parse(String str) {
  int i = 0;
  int strlen = str.length;

// skip leading whitespace
  String strTrim = str.trimLeft();

//while ( Character.isWhitespace(str.charAt(i)))
//i++;

// check for sign
  bool isNegative = false;
  if (i < strlen) {
    String signCh = strTrim[i];
    if (signCh == '-' || signCh == '+') {
      i++;
      if (signCh == '-') isNegative = true;
    }
  }

// scan all digits and accumulate into an integral value
// Keep track of the location of the decimal point (if any) to allow scaling later
  DD val = new DD.empty();

  int numDigits = 0;
  int numBeforeDec = 0;
  int exp = 0;
  bool hasDecimalChar = false;
  while (true) {
    if (i >= strlen) break;
    String ch = str[i];
    i++;
    if (StringUtils.isDigit(ch, 0)) {
      double d = (ch.codeUnitAt(0) - '0'.codeUnitAt(0)).toDouble();
      val.selfMultiplyDD(TEN);
// MD: need to optimize this
      val.selfAdd(d);
      numDigits++;
      continue;
    }
    if (ch == '.') {
      numBeforeDec = numDigits;
      hasDecimalChar = true;
      continue;
    }
    if (ch == 'e' || ch == 'E') {
      String expStr = str.substring(i);
// this should catch any format problems with the exponent
      try {
        exp = int.parse(expStr);
      } catch (ex) {
        throw new ArgumentError("Invalid exponent $expStr in string $str");
      }
      break;
    }
    throw new ArgumentError(
        "Unexpected character '$ch' at position $i in string $str");
  }
  DD val2 = val;

// correct number of digits before decimal sign if we don't have a decimal sign in the string
  if (!hasDecimalChar) numBeforeDec = numDigits;

// scale the number correctly
  int numDecPlaces = numDigits - numBeforeDec - exp;
  if (numDecPlaces == 0) {
    val2 = val;
  } else if (numDecPlaces > 0) {
    DD scale = TEN.pow(numDecPlaces);
    val2 = val.divideDD(scale);
  } else if (numDecPlaces < 0) {
    DD scale = TEN.pow(-numDecPlaces);
    val2 = val.multiplyDD(scale);
  }
// apply leading sign, if any
  if (isNegative) {
    return val2.negate();
  }
  return val2;
}