1 files changed, 38 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/eval_if.cpp b/src/boost/libs/hana/example/eval_if.cpp
new file mode 100644
index 00000000..60aeef42
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+++ b/src/boost/libs/hana/example/eval_if.cpp
@@ -0,0 +1,38 @@
+// 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/config.hpp>
+#include <boost/hana/equal.hpp>
+#include <boost/hana/eval_if.hpp>
+#include <boost/hana/lazy.hpp>
+#include <boost/hana/traits.hpp>
+#include <boost/hana/type.hpp>
+namespace hana = boost::hana;
+
+
+// eval_if with heterogeneous branches and a Constant condition
+BOOST_HANA_CONSTEXPR_LAMBDA auto safe_make_unsigned = [](auto t) {
+    return hana::eval_if(hana::traits::is_integral(t),
+        hana::make_lazy(hana::traits::make_unsigned)(t),
+        hana::make_lazy(t)
+    );
+};
+
+BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<void>) == hana::type_c<void>);
+BOOST_HANA_CONSTANT_CHECK(safe_make_unsigned(hana::type_c<int>) == hana::type_c<unsigned int>);
+
+
+// eval_if with homogeneous branches and a constexpr or runtime condition
+BOOST_HANA_CONSTEXPR_LAMBDA auto safe_divide = [](auto x, auto y) {
+    return hana::eval_if(y == 0,
+        [=](auto) { return 0; },
+        [=](auto _) { return _(x) / y; }
+    );
+};
+
+int main() {
+    BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 3) == 2);
+    BOOST_HANA_CONSTEXPR_CHECK(safe_divide(6, 0) == 0);
+}