diff options
Diffstat (limited to 'src/boost/libs/hana/example/lazy/comonad.cpp')
-rw-r--r-- | src/boost/libs/hana/example/lazy/comonad.cpp | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/lazy/comonad.cpp b/src/boost/libs/hana/example/lazy/comonad.cpp new file mode 100644 index 000000000..39bbbea6b --- /dev/null +++ b/src/boost/libs/hana/example/lazy/comonad.cpp @@ -0,0 +1,30 @@ +// 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/eval.hpp> +#include <boost/hana/extend.hpp> +#include <boost/hana/extract.hpp> +#include <boost/hana/lazy.hpp> + +#include <sstream> +namespace hana = boost::hana; + + +int main() { + std::stringstream s("1 2 3"); + auto i = hana::make_lazy([&] { + int i; + s >> i; + return i; + })(); + + auto i_plus_one = hana::extend(i, [](auto lazy_int) { + return hana::eval(lazy_int) + 1; + }); + + BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 2); + BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 3); + BOOST_HANA_RUNTIME_CHECK(hana::extract(i_plus_one) == 4); +} |