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

Subject: Re: [boost] [histogram] should some_axis::size() return unsigned or int?
From: Emil Dotchevski (emildotchevski_at_[hidden])
Date: 2018-11-30 00:10:37

On Thu, Nov 29, 2018 at 3:38 PM Gavin Lambert via Boost <
boost_at_[hidden]> wrote:
>
> On 30/11/2018 06:12, Hans Dembinski wrote:
> > This is not a good match here, because -1 here does not have the
meaning of "value is missing", but it really is the logical index for the
virtual bin that spans from -infinity to the lower edge of the first bin in
the axis.
> >
> > Value arrow:
> > -inf ——————— | ——————— | —————— | —————— |—————————> +inf
> >        bin -1    bin 0     bin 1    bin 2    bin 3
> >
> > I think representing the underflow bin with -1 and the overflow bin
with the value returned by size() is very intuitive and elegant.
>
> Conventionally your size_type should be the same type returned by size()
> and used for indexing.  So I would expect that type to be int, given the
> above.
>
> Having said that, you're already departing from standard container
> conventions by having size() return a number that is *sometimes* 2
> smaller than the "real" number of bins, which might frustrate generic
> algorithms.
>
> Completely without tongue in cheek, I wonder if it might be better to
> not provide a size() method at all (to avoid container implications
> which you do not satisfy) and spell it as bin_count() or something
> distinct instead.

+1

If the operation differs semantically from .size() in standard containers,
then it shouldn't be called size().