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hana/example/monad/tap.cpp
2014-08-25 12:33:49 -04:00

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794 B
C++

/*
@copyright Louis Dionne 2014
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/detail/assert.hpp>
#include <boost/hana/foreign.hpp>
#include <boost/hana/tuple.hpp>
#include <sstream>
using namespace boost::hana;
int main() {
//! [main]
std::stringstream before, after;
auto xs = tuple(1, 2, 3)
| tap<Tuple>([&](auto x) { before << x << ' '; })
| [](auto x) { return tuple(x, -x); }
| tap<Tuple>([&](auto x) { after << x << ' '; });
BOOST_HANA_RUNTIME_ASSERT(before.str() == "1 2 3 ");
BOOST_HANA_RUNTIME_ASSERT(after.str() == "1 -1 2 -2 3 -3 ");
BOOST_HANA_RUNTIME_ASSERT(xs == tuple(1, -1, 2, -2, 3, -3));
//! [main]
}