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41 lines
1.2 KiB
C++
41 lines
1.2 KiB
C++
/*
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@copyright Louis Dionne 2014
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#include <boost/hana/detail/constexpr.hpp>
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#include <boost/hana/detail/static_assert.hpp>
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#include <boost/hana/integral.hpp>
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#include <boost/hana/list.hpp>
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#include <boost/hana/logical.hpp>
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#include <cassert>
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#include <sstream>
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#include <string>
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using namespace boost::hana;
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int main() {
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//! [fusion]
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auto to_string = [](auto x) { return (std::ostringstream{} << x).str(); };
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auto show = [=](auto x, auto y) {
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return "(" + to_string(x) + " + " + to_string(y) + ")";
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};
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assert(foldr(show, "4", list(1, "2", '3')) == "(1 + (2 + (3 + 4)))");
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//! [fusion]
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//! [mpl]
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BOOST_HANA_CONSTEXPR_LAMBDA auto numbers = list_c<int, 5, -1, 0, -7, -2, 0, -5, 4>;
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BOOST_HANA_CONSTEXPR_LAMBDA auto negatives = list_c<int, -1, -7, -2, -5>;
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BOOST_HANA_CONSTEXPR_LAMBDA auto keep_negatives = [](auto n, auto acc) {
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return if_(n < int_<0>, cons(n, acc), acc);
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};
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BOOST_HANA_STATIC_ASSERT(foldr(keep_negatives, list_c<int>, numbers) == negatives);
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//! [mpl]
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}
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