Re: [boost] [unnullable_ptr] Proposal for a new library

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-07-25 19:52:37

AMDG

Mathias Gaunard wrote:
> Giovanni Piero Deretta wrote:
>   
>> I think that the biggest problem is that, if T is movable,  you cannot
>> statically guarantee that T is never accessed in an empty state, so
>> the never empty guarantee is not as useful.
>>     
>
> You can only move from rvalues.
> Rvalues cannot be accessed later on.
>
> If they're not real rvalues, that means casting was used. Which should
> then make it explicit that trying to access it later on is undefined
> behaviour as far as the implementation of the type is concerned.
>   

Such a move would be much too limiting.
Consider how std::remove would be implemented (untested):

template<class Iter, class T>
Iter remove(Iter begin, Iter end, const T& value) {
    begin = std::find(begin, end, value);
    Iter write_pos = begin++;
    for(; begin != end; ++begin) {
        if(*begin != value) {
            *write_pos++ = std::move(*begin);
        }
    }
    return(write_pos);
}

In Christ,
Steven Watanabe