anchor.diff:    int loopCounter = 0;
     int rangeCounter = 0;
     int counter = 0;
  -  int fc = 0;
  -  int gc = 0;
  +  int fgc = 0;
   
     Type intType = new BuiltInTypeSymbol("int");
     Type vecType = new BuiltInTypeSymbol("vector");
  
positive.code: @after {
  currentScope = currentScope.getEnclosingScope();
  }
    : ^(FILT VARNUM { fc++; currentScope.define(new VarSymbol($VARNUM.text, intType, fc)); } op1=expression op2=expression)
    ;
  
  generator returns [int c]
  
negative.code: @after {
  currentScope = currentScope.getEnclosingScope();
  }
    : ^(GEN VARNUM { fgc++; currentScope.define(new VarSymbol($VARNUM.text, vecType, fgc)); } op1=expression op2=expression)
    {
      counter++;
      $c = counter;
  