Re: [boost] [histogram] should some_axis::size() return unsigned or int?

Subject: Re: [boost] [histogram] should some_axis::size() return unsigned or int?
From: Gavin Lambert (boost_at_[hidden])
Date: 2018-12-03 00:15:48

On 30/11/2018 20:43, Olaf van der Spek wrote:
> Not really: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1227r0.html

Isn’t that proposed definition of ssize() essentially identical to

     // member function
     constexpr difference_type ssize() const
     { return std::distance(begin(), end()); }
     // or moral equivalent, for containers that can implement it
     // more efficiently another way.

     // non-member function in std::
     template <class C>
     constexpr auto ssize(const C& c)
     { return distance(begin(c), end(c)); }
     // or calling member ssize() if it exists

The above seems "better" in that it allows a container intended 
exclusively for small sizes to use a difference_type smaller than ptrdiff_t.

(In the text it explains why it's a bad idea for a container using 
uint16_t sizes with more than 32767 elements to use int16_t as a 
difference_type, but as I understand it that's already undefined 
behaviour -- size_type is required to be larger than difference_type and 
difference_type should be able to express std::distance(begin(), end()) 
or some algorithms will break.)