lispnumber.java

计算机代数系统

package net.sf.yacas;


class LispNumber extends LispObject
{
    /// constructors:
    /// construct from another LispNumber
    public LispNumber(BigNumber aNumber,String aString)
	{
	  iString = aString;
	  iNumber = aNumber;
	}
    /// construct from a BigNumber; the string representation will be absent
    public LispNumber(BigNumber aNumber)
	{
	  iString = null;
	  iNumber =aNumber;
	}
	/// construct from a decimal string representation (also create a number object) and use aBasePrecision decimal digits 
    public LispNumber(String aString, int aBasePrecision)
	{
	  iString = aString;
	  iNumber = null;	// purge whatever it was
	  // create a new BigNumber object out of iString, set its precision in digits
//TODO FIXME enable this in the end	  Number(aBasePrecision);
	}
	public LispObject Copy(boolean aRecursed)
	{
    return new LispNumber(iNumber, iString);
	}
    /// return a string representation in decimal with maximum decimal precision allowed by the inherent accuracy of the number
    public String String() throws Exception
 	  {
	  if (iString == null)
	  {
      LispError.LISPASSERT(iNumber != null);	// either the string is null or the number but not both
      iString = iNumber.ToString(0/*TODO FIXME*/,10);
		// export the current number to string and store it as LispNumber::iString
	  }
	  return iString;
	}
    /// give access to the BigNumber object; if necessary, will create a BigNumber object out of the stored string, at given precision (in decimal?)
    public BigNumber Number(int aPrecision) throws Exception
	{
	  if (iNumber == null)
	  {	// create and store a BigNumber out of string
      LispError.LISPASSERT(iString != null);
      String str;
      str = iString;
      // aBasePrecision is in digits, not in bits, ok
      iNumber = new BigNumber(str, aPrecision, 10/*TODO FIXME BASE10*/);
	  }

	  // check if the BigNumber object has enough precision, if not, extend it
	  // (applies only to floats). Note that iNumber->GetPrecision() might be < 0

	  else if (!iNumber.IsInt() && iNumber.GetPrecision() < aPrecision)
	  {
      if (iString != null)
      {// have string representation, can extend precision
        iNumber.SetTo(iString,aPrecision, 10);
      }
      else
      {
      // do not have string representation, cannot extend precision!
      }
	  }

	  return iNumber;
	}
    /// annotate
    public LispObject SetExtraInfo(LispPtr aData)
	{
	  /*TODO FIXME
		LispObject* result = NEW LispAnnotatedObject<LispNumber>(this);
		result->SetExtraInfo(aData);
		return result;
	  */
	  return null;
	}
    /// number object; NULL if not yet converted from string
    BigNumber iNumber;
    /// string representation in decimal; NULL if not yet converted from BigNumber
    String iString;
};