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Re: Why doesn't iter_swap use swap?

Gabriel Dos Reis wrote:

chris jefferson <> writes:

| >The usual convervative approach is to assume that if it is there then
| >someone may have used it.  Then it is a matter of whether you want to
| >take the blame of breaking a working code -- there might be good
| >reasons to do so.
| >
| >
| If we decided changing iter_swap was too serious an undertaking at
| this point, then according to the standard, should we be using swap()
| or iter_swap() in our implementation of reverse/sort/etc.etc.? I read
| it as swap personally. If we changed iter_swap it would make no
| difference as iter_swap would just call swap. If not, then it might be
| necessary to remove mentions of std::iter_swap(a,b) for swap(*a,*b) so
| we meet requirements?

Arguments can be constructed for either sides.  I personnaly believe
that iter_swap should just defer to swap(), thereby providing a point
of customization.  Of course, that may mean inconveniencing some
religious anti-ADL camps.

Ah, I didn't realise that there was religious anti-ADL types :) I would have thought that you'd definatly want some way to over-ride swap and iter_swap.. but that sounds like a much more large-ranging issue than just this.

For now, to get around the problem of having iter_swap able to take multiple types, how about something like the code below (this is just proof of principle, not serious code ^_^ ). This will call swap() whenever the types are the same, but if anyone is still using different types, it will just call the old inefficent iter_swap(). This should avoid breaking existing code at least? (except now more swaps might get called.


#include<iterator> using namespace std;

template<class T,class U>
struct __iter_swap_helper { static void swapy(const T& t,const U& u) {old_iter_swap(t,u);}

template<class T>
struct __iter_swap_helper<T,T> { static void swapy(const T& t,const T& u) {swap(*t,*u);}

template<class T,class U>
void new_iter_swap(const T &t,const U &u) {

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