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Re: Question about SubRange. [message #49218 is a reply to message #49191]

Mon, 08 January 2018 11:52

mirek
Messages: 13975
Registered: November 2005

Ultimate Member

Novo wrote on Thu, 04 January 2018 21:58

Function SubRange has two overloads below.
template <class C>
auto SubRange(C& c, int pos, int count) -> decltype(SubRange(c.begin() + pos, count))
{
	return SubRange(c.begin() + pos, count);
}

template <class C>
auto SubRange(C&& c, int pos, int count) -> decltype(SubRange(c.begin() + pos, count))
{
	return SubRange(c.begin() + pos, count);
}
The second one doesn't actually move anything, so, it is just not needed, IMHO.
The first one can always be used instead. And it should look like below. IMHO.
template <class C>
auto SubRange(const C& c, int pos, int count) -> decltype(SubRange(c.begin() + pos, count))
{
	return SubRange(c.begin() + pos, count);
}
Method begin() is always const I believe ...

Not true (not in U++ nor STL). That is basically a reason for those 2 overloads. E.g. try Sort with just const variant...

Quote:

And you can drop this decltype in C++14 ...

Not if we want to maintain C++11 compatibility (current status is that we do and we will as long as it is cheap. I think decltype here is cheap).

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