void acc_expand(){
  int len=digits.length;
  int oldOnes[]=digits;
  digits=new int[len + 1];
  System.arraycopy(oldOnes,0,digits,1,len);
}

void acc_expand ( ) { int len = digits . length ; int oldOnes [ ] = digits ; digits = new int [ len + 1 ] ; System . arraycopy ( oldOnes , 0 , digits , 1 , len ) ; }
expand by one and release past ( internal ) memory . this works internally without affecting the outer type pointer .
