Re: [boost] is_pointer Bug

From: Jesse Jones (jesjones_at_[hidden])
Date: 2000-10-15 20:34:55

>Jesse,
>
>>But what if the type is "char* const"? It won't match the specialization
>>because the pointer itself is const. I think there should be a second
>>specialization that looks like this:
>
>That was how it was in one of the early (pre-release) versions, but was
>changed to follow the definitions in 3.9.2 (compound types).  

I'm sure you've already thrashed this out so I don't want to re-open a 
long ago discussion, but I feel obligated to say this much: 

1) I see nothing in sections 3.9.2 and 3.9.3 that make this sensible. The 
closest I can find is the bit at the start of 3.9.3 that says that the 
cv-qualified and cv-unqualified versions of a type are distinct types. 
So, char* and char* const are distinct types, but they're still both 
pointers. 

2) I expect that many people will be surprised to find that is_pointer 
returns false for const pointers. So, it's important that this be well 
documented (see below). It also wouldn't hurt to include a comment in the 
code.

>BTW the docs
>make it clear that is_pointer applies to cv-unqualified types, 

Where? The type_traits.htm file merely says "True if T is a regular 
pointer type - including function pointers - but excluding pointers to 
member functions (3.9.2 p1 and 8.3.1)." This might be sort of clear if 
"Regular pointers" were defined by the standard, but they're not. As far 
as I'm concerned a char* const *is* a regular pointer.

  -- Jesse