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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:45:59 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:45:59 +0000 |
commit | 19fcec84d8d7d21e796c7624e521b60d28ee21ed (patch) | |
tree | 42d26aa27d1e3f7c0b8bd3fd14e7d7082f5008dc /src/boost/libs/hana/example/lazy/monad.cpp | |
parent | Initial commit. (diff) | |
download | ceph-19fcec84d8d7d21e796c7624e521b60d28ee21ed.tar.xz ceph-19fcec84d8d7d21e796c7624e521b60d28ee21ed.zip |
Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/boost/libs/hana/example/lazy/monad.cpp')
-rw-r--r-- | src/boost/libs/hana/example/lazy/monad.cpp | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/lazy/monad.cpp b/src/boost/libs/hana/example/lazy/monad.cpp new file mode 100644 index 000000000..f425e2810 --- /dev/null +++ b/src/boost/libs/hana/example/lazy/monad.cpp @@ -0,0 +1,47 @@ +// Copyright Louis Dionne 2013-2017 +// 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/chain.hpp> +#include <boost/hana/eval.hpp> +#include <boost/hana/lazy.hpp> + +#include <functional> +#include <iostream> +#include <sstream> +namespace hana = boost::hana; + + +template <typename T> +T read_(std::istream& stream) { + T x; + stream >> x; + std::cout << "read " << x << " from the stream\n"; + return x; +} + +int main() { + std::stringstream ss; + int in = 123; + + std::cout << "creating the monadic chain...\n"; + auto out = hana::make_lazy(read_<int>)(std::ref(ss)) + | [](auto x) { + std::cout << "performing x + 1...\n"; + return hana::make_lazy(x + 1); + } + | [](auto x) { + std::cout << "performing x / 2...\n"; + return hana::make_lazy(x / 2); + }; + + std::cout << "putting " << in << " in the stream...\n"; + ss << in; // nothing is evaluated yet + + std::cout << "evaluating the monadic chain...\n"; + auto eout = hana::eval(out); + + std::cout << "the result of the monadic chain is " << eout << "\n"; + BOOST_HANA_RUNTIME_CHECK(eout == (in + 1) / 2); +} |