1 files changed, 66 insertions, 0 deletions
diff --git a/src/boost/libs/hana/example/misc/printf.cpp b/src/boost/libs/hana/example/misc/printf.cpp
new file mode 100644
index 000000000..01f5a9abf
--- /dev/null
+++ b/src/boost/libs/hana/example/misc/printf.cpp
@@ -0,0 +1,66 @@
+// 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/adjust_if.hpp>
+#include <boost/hana/at_key.hpp>
+#include <boost/hana/core/is_a.hpp>
+#include <boost/hana/core/to.hpp>
+#include <boost/hana/filter.hpp>
+#include <boost/hana/functional/compose.hpp>
+#include <boost/hana/functional/partial.hpp>
+#include <boost/hana/map.hpp>
+#include <boost/hana/not.hpp>
+#include <boost/hana/pair.hpp>
+#include <boost/hana/prepend.hpp>
+#include <boost/hana/string.hpp>
+#include <boost/hana/sum.hpp>
+#include <boost/hana/tuple.hpp>
+#include <boost/hana/type.hpp>
+#include <boost/hana/unpack.hpp>
+
+#include <cstdio>
+namespace hana = boost::hana;
+
+
+constexpr auto formats = hana::make_map(
+    hana::make_pair(hana::type_c<int>, hana::string_c<'%', 'd'>),
+    hana::make_pair(hana::type_c<float>, hana::string_c<'%', 'f'>),
+    hana::make_pair(hana::type_c<char const*>, hana::string_c<'%', 's'>)
+);
+
+template <typename ...Tokens>
+constexpr auto format(Tokens ...tokens_) {
+    auto tokens = hana::make_tuple(tokens_...);
+
+    // If you don't care about constexpr-ness of `format`, you can use
+    // this lambda instead of `compose(partial(...), typeid_)`:
+    //
+    // [](auto token) {
+    //     return formats[typeid_(token)];
+    // }
+    auto format_string_tokens = hana::adjust_if(tokens,
+        hana::compose(hana::not_, hana::is_a<hana::string_tag>),
+        hana::compose(hana::partial(hana::at_key, formats), hana::typeid_)
+    );
+
+    auto format_string = hana::sum<hana::string_tag>(format_string_tokens);
+    auto variables = hana::filter(tokens, hana::compose(hana::not_, hana::is_a<hana::string_tag>));
+    return hana::prepend(variables, format_string);
+}
+
+int main() {
+    int a = 1;
+    float b = 1.3;
+    char const* c = "abcdef";
+
+    auto args = format(
+          BOOST_HANA_STRING("first="), a
+        , BOOST_HANA_STRING(" second="), b
+        , BOOST_HANA_STRING(" third="), c
+    );
+
+    hana::unpack(args, [](auto fmt, auto ...args) {
+        std::printf(hana::to<char const*>(fmt), args...);
+    });
+}