From 34946d2ae25a1e113c23c6ead3c55224695a7bbf Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Mon, 17 Jul 2017 20:14:43 +0300
Subject: [PATCH] Add mp_is_map

---
 doc/html/mp11.html         | 12 ++++++++
 doc/mp11/map.adoc          |  6 ++++
 include/boost/mp11/map.hpp | 30 +++++++++++++++++++
 test/Jamfile               |  1 +
 test/mp_is_map.cpp         | 59 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 108 insertions(+)
 create mode 100644 test/mp_is_map.cpp

diff --git a/doc/html/mp11.html b/doc/html/mp11.html
index f3d216a..367185b 100644
--- a/doc/html/mp11.html
+++ b/doc/html/mp11.html
@@ -558,6 +558,7 @@ body.book #toc,body.book #preamble,body.book h1.sect0,body.book .sect1>h2{page-b
 </li>
 <li><a href="#map">Map Operations, &lt;boost/mp11/map.hpp&gt;</a>
 <ul class="sectlevel3">
+<li><a href="#mp_is_map_m">mp_is_map&lt;M&gt;</a></li>
 <li><a href="#mp_map_find_m_k">mp_map_find&lt;M, K&gt;</a></li>
 <li><a href="#mp_map_contains_m_k">mp_map_contains&lt;M, K&gt;</a></li>
 <li><a href="#mp_map_insert_m_t">mp_map_insert&lt;M, T&gt;</a></li>
@@ -3440,6 +3441,17 @@ Only <code>constexpr</code> on C++14 and higher.</p>
 <p>A map is a list of lists, the inner lists having at least one element (the key.) The keys of the map must be unique.</p>
 </div>
 <div class="sect3">
+<h4 id="mp_is_map_m">mp_is_map&lt;M&gt;</h4>
+<div class="literalblock">
+<div class="content">
+<pre>template&lt;class M&gt; using mp_is_map = /*...*/;</pre>
+</div>
+</div>
+<div class="paragraph">
+<p><code>mp_is_map&lt;M&gt;</code> is <code>mp_true</code> if <code>M</code> is a map, <code>mp_false</code> otherwise.</p>
+</div>
+</div>
+<div class="sect3">
 <h4 id="mp_map_find_m_k">mp_map_find&lt;M, K&gt;</h4>
 <div class="literalblock">
 <div class="content">
diff --git a/doc/mp11/map.adoc b/doc/mp11/map.adoc
index ac7d59d..3358eb4 100644
--- a/doc/mp11/map.adoc
+++ b/doc/mp11/map.adoc
@@ -15,6 +15,12 @@ http://www.boost.org/LICENSE_1_0.txt
 
 A map is a list of lists, the inner lists having at least one element (the key.) The keys of the map must be unique.
 
+## mp_is_map<M>
+
+    template<class M> using mp_is_map = /*...*/;
+
+`mp_is_map<M>` is `mp_true` if `M` is a map, `mp_false` otherwise.
+
 ## mp_map_find<M, K>
 
     template<class M, class K> using mp_map_find = /*...*/;
diff --git a/include/boost/mp11/map.hpp b/include/boost/mp11/map.hpp
index 85e233a..b1ced45 100644
--- a/include/boost/mp11/map.hpp
+++ b/include/boost/mp11/map.hpp
@@ -13,6 +13,8 @@
 #include <boost/mp11/integral.hpp>
 #include <boost/mp11/utility.hpp>
 #include <boost/mp11/algorithm.hpp>
+#include <boost/mp11/function.hpp>
+#include <boost/mp11/set.hpp>
 #include <type_traits>
 
 namespace boost
@@ -82,6 +84,34 @@ template<class M, class K> using mp_map_erase = typename detail::mp_map_erase_im
 // mp_map_keys<M>
 template<class M> using mp_map_keys = mp_transform<mp_first, M>;
 
+// mp_is_map<M>
+namespace detail
+{
+
+template<class L> struct mp_is_map_element: mp_false
+{
+};
+
+template<template<class...> class L, class T1, class... T> struct mp_is_map_element<L<T1, T...>>: mp_true
+{
+};
+
+template<class M> using mp_keys_are_set = mp_is_set<mp_map_keys<M>>;
+
+template<class M> struct mp_is_map_impl
+{
+    using type = mp_false;
+};
+
+template<template<class...> class M, class... T> struct mp_is_map_impl<M<T...>>
+{
+    using type = mp_eval_if<mp_not<mp_all<mp_is_map_element<T>...>>, mp_false, mp_keys_are_set, M<T...>>;
+};
+
+} // namespace detail
+
+template<class M> using mp_is_map = typename detail::mp_is_map_impl<M>::type;
+
 } // namespace mp11
 } // namespace boost
 
diff --git a/test/Jamfile b/test/Jamfile
index 308036b..210a3da 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -124,6 +124,7 @@ run mp_map_replace.cpp : : : $(REQ) ;
 run mp_map_erase.cpp : : : $(REQ) ;
 run mp_map_update.cpp : : : $(REQ) ;
 run mp_map_keys.cpp : : : $(REQ) ;
+run mp_is_map.cpp : : : $(REQ) ;
 
 # bind
 run mp_bind.cpp : : : $(REQ) ;
diff --git a/test/mp_is_map.cpp b/test/mp_is_map.cpp
new file mode 100644
index 0000000..980d140
--- /dev/null
+++ b/test/mp_is_map.cpp
@@ -0,0 +1,59 @@
+
+// Copyright 2017 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/map.hpp>
+#include <boost/mp11/list.hpp>
+#include <boost/mp11/integral.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <tuple>
+#include <utility>
+
+int main()
+{
+    using boost::mp11::mp_is_map;
+    using boost::mp11::mp_list;
+    using boost::mp11::mp_true;
+    using boost::mp11::mp_false;
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<void>, mp_false>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<>>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<void>>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<void>>, mp_false>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<mp_list<>>>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::tuple<>>>, mp_false>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<mp_list<int>>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::tuple<int>>>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<std::pair<int, int const>>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::pair<int, int const>>>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<std::pair<int, int const>, std::pair<long, long const>>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::pair<int, int const>, std::pair<long, long const>>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::pair<std::pair<int, int const>, std::pair<long, long const>>>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<std::pair<int, int const>, std::pair<int, long const>>>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::pair<int, int const>, std::pair<int, long const>>>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::pair<std::pair<int, int const>, std::pair<int, long const>>>, mp_false>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<mp_list<int>, mp_list<long, long>, mp_list<long long, long long, long long>>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<mp_list<int>, mp_list<long, long>, mp_list<long long, long long, long long>>>, mp_true>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::tuple<int>, std::pair<long, long>, std::tuple<long long, long long, long long>>>, mp_true>));
+
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<mp_list<mp_list<int>, mp_list<long, long>, mp_list<int, long long, long long>>>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<mp_list<int>, mp_list<long, long>, mp_list<int, long long, long long>>>, mp_false>));
+    BOOST_TEST_TRAIT_TRUE((std::is_same<mp_is_map<std::tuple<std::tuple<int>, std::pair<long, long>, std::tuple<int, long long, long long>>>, mp_false>));
+
+    return boost::report_errors();
+}