The content of this blog is my personal opinion only. Although I am an employee - currently of Nvidia, in the past of other companies such as Iagination Technologies, MIPS, Intellectual Ventures, Intel, AMD, Motorola, and Gould - I reveal this only so that the reader may account for any possible bias I may have towards my employer's products. The statements I make here in no way represent my employer's position, nor am I authorized to speak on behalf of my employer. In fact, this posting may not even represent my personal opinion, since occasionally I play devil's advocate.

See http://docs.google.com/View?id=dcxddbtr_23cg5thdfj for photo credits.

Thursday, May 10, 2012

Disambiguating names according to scopes in C++

int biff;
int var;
struct Var {
  int var;
  void foo(int var) {
      biff = var; 
Which var is used in the assignment? Sure, a good C++ programmer knows the rules. But it can be hard to tell in a large program. You can disambiguate for the member
      biff = this->var; 
or the global
      biff = ::var; 
But so far as I know there is no syntax for arguments. I often use a naming convention
  void foo(int arg_var) {
      this->var = arg_var; 
This is not unlike the widespread convention of saying
  void foo(int arg_var) {
      m_var = arg_var; 
although I deprecate this because m_var for member names can lie - there may be a global of that name. Whereas this-> is not much bigger, and has the compiler check your meaning. Perhaps there should be sigils, like this-> and ::, for arguments and locals? -- Late addition, 5/25/2012: I dislike extra typing. Plus, occasionally I will do a refactoring where an arg or a global becomes a local or a member. Sometimes I want such refactorfings to show up in history diffs, sometimes not. Here's an interesting possibility: have the build or ODE system annotate the code with a hidden sigil (which I would suggest being XML, something like . Have the IDE warn if an edit would change the implicit sigil. Much as GCC warns if an inner scope hides an outer scope's name.

No comments: