fold.cpp
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// Copyright Louis Dionne 2013-2022
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
#include <boost/hana/assert.hpp>
#include <boost/hana/fold.hpp>
#include <boost/hana/tuple.hpp>
#include <sstream>
#include <string>
namespace hana = boost::hana;
auto to_string = [](auto x) {
std::ostringstream ss;
ss << x;
return ss.str();
};
int main() {
auto f = [=](std::string s, auto element) {
return "f(" + s + ", " + to_string(element) + ")";
};
// with an initial state
BOOST_HANA_RUNTIME_CHECK(
hana::fold(hana::make_tuple(2, '3', 4, 5.0), "1", f)
==
"f(f(f(f(1, 2), 3), 4), 5)"
);
// without initial state
BOOST_HANA_RUNTIME_CHECK(
hana::fold(hana::make_tuple("1", 2, '3', 4, 5.0), f)
==
"f(f(f(f(1, 2), 3), 4), 5)"
);
}