Free Hero Mesh

static inline Uint32 chebyshev(Uint32 a,Uint32 b) {
  Uint32 i,j;
  if(a==VOIDLINK || b==VOIDLINK) return 0;
  i=abs(objects[a]->x-objects[b]->x);
  j=abs(objects[a]->y-objects[b]->y);
  return i>j?i:j;
}

static inline void v_flip(void) {
  int p=vstackptr;
  int n;
  Value v;
  while(p-- && vstack[p].t!=TY_MARK);
  if(!p) Throw("No mark");
  p++;
  for(n=0;n<(vstackptr-p)/2;n++) {
    v=vstack[p+n];
    vstack[p+n]=vstack[vstackptr-n-1];
    vstack[vstackptr-n-1]=v;
  }
}

// Here is where the execution of a Free Hero Mesh bytecode subroutine is executed.
#define NoIgnore() do{ changed=1; }while(0)
#define GetVariableOf(a,b) (i=v_object(Pop()),i==VOIDLINK?NVALUE(0):b(objects[i]->a))
#define GetVariableOrAttributeOf(a,b) (t2=Pop(),t2.t==TY_CLASS?NVALUE(classes[t2.u]->a):(i=v_object(t2),i==VOIDLINK?NVALUE(0):b(objects[i]->a)))
#define Numeric(a) do{ if((a).t!=TY_NUMBER) Throw("Type mismatch"); }while(0)
#define DivideBy(a) do{ Numeric(a); if(!(a).u) Throw("Division by zero"); }while(0)

    case OP_DONE_EC: StackReq(2,0); SetFlagOf(OF_DONE); break;
    case OP_DROP: StackReq(1,0); Pop(); break;
    case OP_DROP_D: StackReq(2,0); Pop(); Pop(); break;
    case OP_DUP: StackReq(1,2); t1=Pop(); Push(t1); Push(t1); break;
    case OP_EQ: StackReq(2,1); t2=Pop(); t1=Pop(); Push(NVALUE(v_equal(t1,t2)?1:0)); break;
    case OP_FINISHED: StackReq(0,1); Push(NVALUE(all_flushed)); break;
    case OP_FINISHED_E: StackReq(1,0); t1=Pop(); Numeric(t1); all_flushed=t1.u; break;
    case OP_FLIP: v_flip(); break;
    case OP_FLUSHCLASS: NoIgnore(); StackReq(1,0); t1=Pop(); if(t1.t==TY_CLASS) flush_class(t1.u); else if(t1.t==TY_NUMBER && t1.s==-1) flush_all(); else if(t1.t) Throw("Type mismatch"); break;
    case OP_FLUSHOBJ: NoIgnore(); flush_object(obj); break;
    case OP_FLUSHOBJ_C: NoIgnore(); StackReq(1,0); i=v_object(Pop()); if(i!=VOIDLINK) flush_object(i); break;
    case OP_FOR: NoIgnore(); StackReq(3,1); t3=Pop(); t2=Pop(); t1=Pop(); ptr=v_for(code,ptr,t1,t2,t3); break;
    case OP_FROM: StackReq(0,1); Push(OVALUE(msgvars.from)); break;
    case OP_FUNCTION: execute_program(classes[0]->codes,functions[code[ptr++]],obj); break;
    case OP_GE: StackReq(2,1); t2=Pop(); t1=Pop(); Push(NVALUE(v_unsigned_greater(t2,t1)?0:1)); break;