procedure TParser6502.visit(aNode : TAST);
begin
  if (aNode is TUnaryOp) then
    visitUnaryOp(TUnaryOp(aNode))
  else if (aNode is TBinOp) then
    visitBinOp(TBinOp(aNode))
  else if (aNode is TNumber) then
    visitNumber(TNumber(aNode))
  else if (aNode is TVariable) then
    visitVariable(TVariable(aNode))
  else if (aNode is TAssign) then
    visitAssign(TAssign(aNode))
  else
    raise Exception.Create('Visit: Unknown AST Node "'+aNode.ClassName+'"');
end;