From beb9c2dd595efb094c0dea8d329a8ea69b82dc39 Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Thu, 14 Feb 2019 19:57:04 +0200
Subject: [PATCH] Add mp_eval_if_not

---
 include/boost/mp11/utility.hpp |  4 +++
 test/Jamfile                   |  1 +
 test/mp_eval_if_not.cpp        | 47 ++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 test/mp_eval_if_not.cpp

diff --git a/include/boost/mp11/utility.hpp b/include/boost/mp11/utility.hpp
index 8a8ee27..b68351a 100644
--- a/include/boost/mp11/utility.hpp
+++ b/include/boost/mp11/utility.hpp
@@ -147,6 +147,10 @@ template<bool C, class T, template<class...> class F, class... U> using mp_eval_
 template<class C, class T, template<class...> class F, class... U> using mp_eval_if = typename detail::mp_eval_if_c_impl<static_cast<bool>(C::value), T, F, U...>::type;
 template<class C, class T, class Q, class... U> using mp_eval_if_q = typename detail::mp_eval_if_c_impl<static_cast<bool>(C::value), T, Q::template fn, U...>::type;
 
+// mp_eval_if_not
+template<class C, class T, template<class...> class F, class... U> using mp_eval_if_not = mp_eval_if<mp_not<C>, T, F, U...>;
+template<class C, class T, class Q, class... U> using mp_eval_if_not_q = mp_eval_if<mp_not<C>, T, Q::template fn, U...>;
+
 // mp_cond
 
 // so elegant; so doesn't work
diff --git a/test/Jamfile b/test/Jamfile
index 7137c5f..437c187 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -124,6 +124,7 @@ run mp_quote_trait.cpp ;
 run mp_cond.cpp ;
 run mp_cond_sf.cpp ;
 run mp_not_fn.cpp ;
+run mp_eval_if_not.cpp ;
 
 # integer_sequence
 run integer_sequence.cpp ;
diff --git a/test/mp_eval_if_not.cpp b/test/mp_eval_if_not.cpp
new file mode 100644
index 0000000..987e037
--- /dev/null
+++ b/test/mp_eval_if_not.cpp
@@ -0,0 +1,47 @@
+
+// Copyright 2015, 2017, 2019 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+
+#include <boost/mp11/utility.hpp>
+#include <boost/mp11/integral.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+
+int main()
+{
+    using boost::mp11::mp_identity;
+    using boost::mp11::mp_eval_if_not;
+    using boost::mp11::mp_eval_if_not_q;
+    using boost::mp11::mp_quote;
+
+    using qt_identity = mp_quote<mp_identity>;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not<std::false_type, char[], mp_identity, void, void, void>, char[]>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not<std::true_type, char[], mp_identity, void()>, mp_identity<void()>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not_q<std::false_type, char[], qt_identity, void, void, void>, char[]>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not_q<std::true_type, char[], qt_identity, void()>, mp_identity<void()>>));
+
+    using boost::mp11::mp_int;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not<mp_int<0>, char[], mp_identity, void, void, void>, char[]>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not<mp_int<-7>, char[], mp_identity, void()>, mp_identity<void()>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not_q<mp_int<0>, char[], qt_identity, void, void, void>, char[]>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not_q<mp_int<-7>, char[], qt_identity, void()>, mp_identity<void()>>));
+
+    using boost::mp11::mp_size_t;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not<mp_size_t<0>, char[], mp_identity, void, void, void>, char[]>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not<mp_size_t<14>, char[], mp_identity, void()>, mp_identity<void()>>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not_q<mp_size_t<0>, char[], qt_identity, void, void, void>, char[]>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_eval_if_not_q<mp_size_t<14>, char[], qt_identity, void()>, mp_identity<void()>>));
+
+    return boost::report_errors();
+}