[boost] [histogram] Working with standard algorithms

Subject: [boost] [histogram] Working with standard algorithms
From: Bjorn Reese (breese_at_[hidden])
Date: 2017-11-18 16:08:51

I would like to see a better integration between boost.histogram and
standard algorithms, especially those from <numeric>. Today they do not
work together because the dereference operator of the axis iterator
returns a pair (index and content) rather than the content.

An example of where standard algorithms could be useful is calculating
the cumulative distribution of a one-dimensional histogram, which ought
to be a simple as:

   auto& axis = h.axis();
   std:partial_sum(axis.begin(), axis.end(), axis.begin());

Another example is ranking a set of histograms based on the cosine
similarity [1] using std::inner_product().

[1] https://en.wikipedia.org/wiki/Cosine_similarity