Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/src/boost/libs/hana/example/chain.cpp b/src/boost/libs/hana/example/chain.cpp
new file mode 100644
index 00000000..0e7850b7
--- /dev/null
+++ b/src/boost/libs/hana/example/chain.cpp
@@ -0,0 +1,41 @@
+// 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/config.hpp>
+#include <boost/hana/equal.hpp>
+#include <boost/hana/optional.hpp>
+namespace hana = boost::hana;
+
+
+BOOST_HANA_CONSTEXPR_LAMBDA auto deref = [](auto x) -> decltype(*x) {
+    return *x;
+};
+
+BOOST_HANA_CONSTEXPR_LAMBDA auto age = [](auto x) -> decltype(x.age) {
+    return x.age;
+};
+
+BOOST_HANA_CONSTEXPR_LAMBDA auto f = [](auto x) {
+    return hana::chain(hana::sfinae(deref)(x), hana::sfinae(age));
+};
+
+struct Person {
+    unsigned int age;
+    // ...
+};
+
+int main() {
+    constexpr Person john{30};
+
+    // Can't dereference a non-pointer.
+    BOOST_HANA_CONSTANT_CHECK(f(john) == hana::nothing);
+
+    // `int` has no member named `age`.
+    BOOST_HANA_CONSTANT_CHECK(f(1) == hana::nothing);
+
+    // All is good.
+    BOOST_HANA_CONSTEXPR_CHECK(f(&john) == hana::just(30u));
+}