protected static Dfp expInternal(final Dfp a){
  Dfp y=a.getOne();
  Dfp x=a.getOne();
  Dfp fact=a.getOne();
  Dfp py=new Dfp(y);
  for (int i=1; i < 90; i++) {
    x=x.multiply(a);
    fact=fact.divide(i);
    y=y.add(x.multiply(fact));
    if (y.equals(py)) {
      break;
    }
    py=new Dfp(y);
  }
  return y;
}

protected static Dfp expInternal ( final Dfp a ) { Dfp y = a . getOne ( ) ; Dfp x = a . getOne ( ) ; Dfp fact = a . getOne ( ) ; Dfp py = new Dfp ( y ) ; for ( int i = 1 ; i < 90 ; i ++ ) { x = x . multiply ( a ) ; fact = fact . divide ( i ) ; y = y . add ( x . multiply ( fact ) ) ; if ( y . equals ( py ) ) { break ; } py = new Dfp ( y ) ; } return y ; }
computes e to the given power . where - 1 < a < 1 . use the classic taylor series . 1 + x * * 2 / 2 ! + x * * 3 / 3 ! + x * * 4 / 4 ! . . .
