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// Copyright 2019 Hans Dembinski
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)
//[ guide_custom_accumulators_ouroboros
#include <boost/histogram.hpp>
#include <cmath>
#include <iostream>
#include <sstream>
#include <string>
int main() {
using namespace boost::histogram;
// First we define the nested histogram type.
using axis_t = axis::category<int, axis::null_type, axis::option::growth_t>;
using base_t = histogram<std::tuple<axis_t>>;
// Now we make an accumulator out of it by using inheritance.
// We only need to implement operator(). A matching version of operator() is actually
// present in base_t, but it is templated and this is not allowed by the accumulator
// concept. Initialization could also happen here. We don't need to initialize anything
// here, because the default constructor of base_t is called automatically and
// sufficient for this example.
struct hist_t : base_t {
void operator()(const double x) { base_t::operator()(x); }
};
auto h = make_histogram_with(dense_storage<hist_t>(), axis::integer<>(1, 4));
auto x = {1, 1, 2, 2};
auto s = {1, 2, 3, 3}; // samples are filled into the nested histograms
h.fill(x, sample(s));
std::ostringstream os;
for (auto&& x : indexed(h)) {
os << x.bin() << " ";
for (auto&& y : indexed(*x)) { os << "(" << y.bin() << ": " << *y << ") "; }
os << "\n";
}
std::cout << os.str() << std::flush;
assert(os.str() == "1 (1: 1) (2: 1) \n"
"2 (3: 2) \n"
"3 \n");
}
//]
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