Free Hero Mesh

object as the origin of the movement, and that object's direction as the
direction of movement.


=== Pattern matching ===

Where an instruction is expected, you can have pattern matching. This can
be (<operator> <pattern...>) where the operator can be one of:
be (P <pattern...>) or (,P <pattern...>) where the first one uses the
current location, and the second kind uses the position and direction of
the specified object as the matching. It pushes the found object to the
stack, or pushes zero if the pattern does not match.

P
  Find starting at the current location, with the current object's
  direction. Pushes the found object, or zero if not found.

,P
  Find starting at the specified object's location and direction. Pushes
  the found object, or zero if not found.

=P
  Searches everywhere. Pushes the found object, or zero if not found.

P*
  Like P but push all found objects, or pushes nothing if not found.

,P*
  Like ,P but push all found objects, or pushes nothing if not found.

=P*
  Like =P but push all found objects, or pushes nothing if not found.

Inside the pattern, the following commands are allowed (although the
commands that push stuff to the stack should not be used in the patterns
with P* or ,P* or =P*):

<class>
  Match an object of the specified class.

<dir>
  Move in the specified direction. (This does not move any objects; it
  only moves the cursor for pattern matching.) The direction can be

    case OP_OBJBOTTOMAT:
      n=obj_bottom_at(x,y);
      break;
    case OP_OBJTOPAT:
      n=obj_top_at(x,y);
      break;
    case OP_RET:
      if(all) {
        if(vstackptr>=VSTACKSIZE-1) Throw("Stack overflow");
        if(n==VOIDLINK) n=obj_bottom_at(x,y);
        Push(OVALUE(n));
        goto fail;
      } else {
      return n==VOIDLINK?obj_bottom_at(x,y):n;
        return n==VOIDLINK?obj_bottom_at(x,y):n;
      }
      break;
    case OP_SUB:
      if(vstackptr>=VSTACKSIZE-1) Throw("Stack overflow");
      Push(NVALUE(0));
      break;
    case OP_THEN:
      // This opcode does nothing
      break;
    case OP_TRACE:
      if(main_options['t']) {
        printf("ptr=%d cpi=%d x=%d y=%d dir=%d obj=%lu ",ptr,cpi,x,y,d,(long)n);
        printf("[ptr=%d x=%d y=%d dir=%d]\n",cp[cpi].ptr,cp[cpi].x,cp[cpi].y,cp[cpi].dir);
      }
      break;
    default: Throw("Unimplemented opcode in pattern");
  }
  goto again;
  fail:
  if(!all) {
  if(vstackptr<cp->depth) Throw("Stack underflow in pattern matching");
  vstackptr=cp[cpi].depth;
    if(vstackptr<cp->depth) Throw("Stack underflow in pattern matching");
    vstackptr=cp[cpi].depth;
  }
  if(!cpi) return VOIDLINK;
  x=cp[cpi].x;
  y=cp[cpi].y;
  d=cp[cpi].dir;
  ptr=cp[cpi].ptr;
  n=VOIDLINK;
  cpi--;
  goto again;
}

static Uint32 v_pattern_anywhere(Uint16*code,int ptr,char all) {
  int i;
  Uint32 n;
  for(i=0;i<pfheight*64;i++) {
    n=playfield[i];
    if(n!=VOIDLINK) {
      n=v_pattern(code,ptr,n,all);
      if(n!=VOIDLINK && !all) return n;
    }
  }
  return VOIDLINK;
}

// 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_OBJDIR_C: StackReq(2,1); t2=Pop(); Numeric(t2); i=obj_dir(v_object(Pop()),t2.u); Push(OVALUE(i)); break;
    case OP_OBJLAYERAT: StackReq(3,1); t3=Pop(); Numeric(t3); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); i=obj_layer_at(t1.u,t2.u,t3.u); Push(OVALUE(i)); break;
    case OP_OBJMOVINGTO: StackReq(2,0); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); v_obj_moving_to(t1.u,t2.u); break;
    case OP_OBJTOPAT: StackReq(2,1); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); i=obj_top_at(t1.u,t2.u); Push(OVALUE(i)); break;
    case OP_OVER: StackReq(2,3); t2=Pop(); t1=Pop(); Push(t1); Push(t2); Push(t1); break;
    case OP_PATTERN: StackReq(0,1); i=code[ptr++]; j=v_pattern(code,ptr,obj,0); ptr=i; Push(OVALUE(j)); break;
    case OP_PATTERN_C: StackReq(1,1); i=code[ptr++]; j=v_object(Pop()); if(j!=VOIDLINK) j=v_pattern(code,ptr,j,0); ptr=i; Push(OVALUE(j)); break;
    case OP_PATTERN_E: StackReq(0,1); i=code[ptr++]; j=v_pattern_anywhere(code,ptr,0); ptr=i; Push(OVALUE(j)); break;
    case OP_PATTERNS: StackReq(0,1); i=code[ptr++]; v_pattern(code,ptr,obj,1); ptr=i; break;
    case OP_PATTERNS_C: StackReq(1,1); i=code[ptr++]; j=v_object(Pop()); if(j!=VOIDLINK) v_pattern(code,ptr,j,1); ptr=i; break;
    case OP_PATTERNS_E: StackReq(0,1); i=code[ptr++]; v_pattern_anywhere(code,ptr,1); ptr=i; break;
    case OP_PICK: StackReq(0,1); t1=Pop(); Numeric(t1); if(t1.u>=vstackptr) Throw("Stack index out of range"); t1=vstack[vstackptr-t1.u-1]; Push(t1); break;
    case OP_PLAYER: StackReq(0,1); if(classes[o->class]->cflags&CF_PLAYER) Push(NVALUE(1)); else Push(NVALUE(0)); break;
    case OP_PLAYER_C: StackReq(1,1); GetClassFlagOf(CF_PLAYER); break;
    case OP_PLUSMOVE: StackReq(1,1); t1=Pop(); Numeric(t1); i=defer_move(obj,t1.u,1); Push(NVALUE(i)); break;
    case OP_PLUSMOVE_C: StackReq(2,1); t1=Pop(); Numeric(t1); i=v_object(Pop()); i=defer_move(i,t1.u,1); Push(NVALUE(i)); break;
    case OP_PLUSMOVE_D: StackReq(1,0); t1=Pop(); Numeric(t1); defer_move(obj,t1.u,1); break;
    case OP_PLUSMOVE_CD: StackReq(2,1); t1=Pop(); Numeric(t1); i=v_object(Pop()); defer_move(i,t1.u,1); break;