Re: [boost] Re: Re: Formal Review: FOREACH macro

From: Dave Harris (brangdon_at_[hidden])
Date: 2005-05-11 12:56:42

In-Reply-To: <00fb01c55599$e9fc23e0$6401a8c0_at_pdimov2>
pdimov_at_[hidden] (Peter Dimov) wrote (abridged):
> I think that defining size( T[N] ) as N or N-1, depending on whether T 
> is a character type, will cause problems in generic code and preclude 
> the widespread use of the library.

I agree.

If we do support null-terminated character strings, can we support other 
kinds of terminators too? (Without undue loss of efficiency.) For example:

     int array[] = { 1, 2, 3, -1 };
     int *pArray = array;
     
     for (int i, terminator_adaptor(pArray,-1))
         cout << i; // Does not write -1.

This can be useful if the size of the array is not visible to for(:).

I use terminators fairly often, usually NULL for pointers, 0 or -1 for 
integral types, and "end" for enums. It's not something specific to 
characters. In fact, for me the need to enumerate character strings is 
rarer than for these other types. Usually strings are either wrapped in 
std::string or similar, or else passed to some other routine.

By "Without undue loss of efficiency" I really mean without scanning the 
sequence an extra time to find the end. My impression is that 
BOOST_FOR_EACH had a fairly general termination mechanism which could cope 
with that.

-- Dave Harris, Nottingham, UK.