In C++ is “const” after type ID acceptable?

Question

My co-worker is 0 for 2 on questions he has inspired (1, 2), so I thought I'd give him a chance to catch up.

Our latest disagreement is over the style issue of where to put "const" on declarations.

He is of the opinion that it should go either in front of the type, or after the pointer. The reasoning is that this is what is typically done by everyone else, and other styles are liable to be confusing. Thus a pointer to a constant int, and a constant pointer to int would be respectively:

const int *i;
      int * const i;

However, I'm confused anyway. I need rules that are consistent and easy to understand, and the only way I can make sense of "const" is that it goes after the thing it is modifying. There's an exception that allows it to go in front of the final type, but that's an exception, so it's easier on me if I don't use it.

Thus a pointer to a constant int, and a constant pointer to int would be respectively:

int const * i;
int * const i;

As an added benefit, doing things this way makes deeper levels of indirection easier to understand. For example, a pointer to a constant pointer to int would clearly be:

int * const * i;

My contention is that if someone just learns it his way, they'll have little trouble figuring out what the above works out to.

The ultimate issue here is that he thinks that putting const after int is so unspeakably ugly, and so harmful to readability that it should be banned in the style guide. Of course, I think if anything the guide should suggest doing it my way, but either way we shouldn't be banning one approach.

Edit: I've gotten a lot of good answers, but none really directly address my last paragraph ("The ultimate issue"). A lot of people argue for consistency, but is that so desirable in this case that it is a good idea to ban the other way of doing it, rather that just discouraging it?

Answer 1

People typically use const int* blah because it reads well as English. I wouldn't underestimate the usefulness of that.

I find that the int* const blah variation is rare enough that it's not typically useful to make the more common definition backwards. I am, in general, not a fan of anything that even slightly obscures code in the general case, though it might provide some nominal benefit in the exceptional case.

See also "if (1 == a)". Some people really enjoy writing code that doesn't read as English. I am not one of those people.

Really, though, the rules behind const are simple. Look to the left, then to the right. So simple that I wouldn't think it's worth much attention in a style guide.

Answer 2

Personally I (and it is a personal preeference) I finding reading type declarations from right to left the easiest. Especially when you start throwing references into the mix.

std::string const&  name = plop; // reference to const string.

const std::string&  flame =plop; // reference to string const;
                                 // That works better if you are German I suppose :-)

Answer 3

Putting "const" after the type declaration makes a whole lot more sense once you train yourself to read your C++ type declarations from right to left.

I'm going to peg your cow-orker at 0-for-3 :)