wheel.c

/*
 * Does it matter legally, if I share this without cause or license?
 */
int16_t wheel( int16_t a, unsigned char b)
{
  int16_t stack[7];
  int16_t tmp;
  int depth;
  enum primitives { end, unfold, dup2, flip, swap, dup, mult, minus,
                    add2, add1 };

  int code[] = { unfold,dup2,flip,swap,dup,mult,swap,dup,mult,
                 minus,swap,minus,mult,add2,swap,add1,mult,flip, end };
  int pc;

  depth=0;
  stack[depth++]=a;
  stack[depth++]=b;
  for (pc=0;  end != code[pc] ; pc++ ) {
    switch(code[pc]) {
    case dup:
      tmp=stack[depth];
      depth++;
      stack[depth]=tmp;
      break;
    case dup2:
      tmp=stack[depth];
      stack[depth+1]=stack[depth-1];
      depth+=2;
      stack[depth]=tmp;
      break;
    case swap:
      tmp=stack[depth];
      stack[depth]=stack[depth-1];
      stack[depth-1]=tmp;
      break;
    case unfold:
      tmp=stack[depth];
      stack[depth]=stack[depth-1];
      depth++;
      stack[depth]=tmp;
      break;
    case flip:
      {
        unsigned char uc;
        union {
          unsigned char uc[2];
          int16_t i;
        } f;
        f.i=stack[depth];
        uc=f.uc[0];
        f.uc[0]=f.uc[1];
        f.uc[1]=uc;
        stack[depth]=f.i;
      }
      break;
    case mult:
      tmp=(stack[depth-1] * stack[depth]);
      depth--;
      stack[depth]=tmp;
      break;
    case minus:
      tmp=(stack[depth-1] - stack[depth]);
      depth--;
      stack[depth]=tmp;
      break;
    case add1:
      stack[depth]++;
      break;
    case add2:
      stack[depth]+=2;
    }
  }
  return stack[depth];
}