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- // Copyright 2018 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_2
- #include <boost/format.hpp>
- #include <boost/histogram.hpp>
- #include <cassert>
- #include <iostream>
- #include <sstream>
- int main() {
- using namespace boost::histogram;
- // Make a custom accumulator, which tracks the maximum of the samples.
- // It must have a call operator that accepts the argument of the `sample` function.
- struct maximum {
- // return value is ignored, so we use void
- void operator()(double x) {
- if (x > value) value = x;
- }
- double value = 0; // value is initialized to zero
- };
- // Create 1D histogram that uses the custom accumulator.
- auto h = make_histogram_with(dense_storage<maximum>(), axis::integer<>(0, 2));
- h(0, sample(1.0)); // sample goes to first cell
- h(0, sample(2.0)); // sample goes to first cell
- h(1, sample(3.0)); // sample goes to second cell
- h(1, sample(4.0)); // sample goes to second cell
- std::ostringstream os;
- for (auto&& x : indexed(h)) {
- os << boost::format("index %i maximum %.1f\n") % x.index() % x->value;
- }
- std::cout << os.str() << std::flush;
- assert(os.str() == "index 0 maximum 2.0\n"
- "index 1 maximum 4.0\n");
- }
- //]
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