Base Conversion - Negative Base

Question

Hello everybody. I am writing a code of Base Conversion. I came to know that there are [Negative base|http://en.wikipedia.org/wiki/Negative_base] too. And I am able to convert fractional number with negative base into decimal and in that link there is an algorithm given to convert decimal to number with negative base, but they all are in integers. If anyone know the procedure/algorithm of converting a fractional decimal number, please let me know, it will be very helpful to me. Thank you.
I am posting the toDecimal() method, however there are other methods too :
public String toDecimal(String numberInInputBase, String inputBase) throws ParseError {
          this.numberInInputBase = numberInInputBase;
          if (inputBase.equals("0") || inputBase.equals("1")) {
               throw new ParseError("Invalid input");
          this.inputBase = inputBase;
          this.lookUpStringForInputBase = lookUpString.substring(0, Math.abs(Integer.parseInt(inputBase)));
          split();
          return toDecimal();
     public String toDecimal() throws ParseError {
          // if the numberInInputBase or inputBase is vacent
          if (numberInInputBase == null || inputBase == null) {
               throw new ParseError("Invalid input");
          BigDecimal output = new BigDecimal(BigInteger.ZERO); // initialize output
          BigDecimal base = new BigDecimal(inputBase); // convert inputBase into BigDecimal
          for (int idx = 0; idx < intPart.length(); idx++) {
               int digit = lookUpStringForInputBase.indexOf(intPart.charAt(idx));
               // intPart.charAt(idx) return charater at a perticular idx and then lookUpStringForInputBase.indexOf return
               // the index of that character
               if (digit != -1) {
                    // if character is found in the String
                    output = output.add(BigDecimal.valueOf(digit).multiply(base.pow(intPartLength--)));
               } else {
                    throw new ParseError("Invalid input");
          if (fracPartLength != 0) {
               int incr = 0;
               for (int idx = 0; idx <= fracPartLength; idx++) {
                    int digit = lookUpStringForInputBase.indexOf(fracPart.charAt(idx));
                    if (digit != -1) {
                         output = output.add(BigDecimal.valueOf(digit).divide(base.pow(++incr), 10, BigDecimal.ROUND_HALF_UP));
                    } else {
                         throw new ParseError("Invalid input");
          this.numberInOutputBase = output.toString();
          return getNumberInOutputBase();
     }Edited by: tapas.23571113 on Aug 2, 2010 4:32 AM

Answer 1

Hi,
Read the javadoc for Integer. There are two methods which you are interested in, parseInt(String s, int radix) and toString(int i, int radix)
Kaj