Add test/mp_compose_sf.cpp (by Jody Hagins in #76.) Fixes #76.

test/Jamfile

@@ -152,6 +152,7 @@ run mp_eval_if_not.cpp ;
 run mp_eval_or.cpp ;
 run mp_compose.cpp ;
 run mp_valid_and_true.cpp ;
+compile mp_compose_sf.cpp ;
 
 # integer_sequence
 run integer_sequence.cpp ;

test/mp_compose_sf.cpp

@@ -0,0 +1,58 @@
+// Copyright 2023 Jody Hagins
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/mp11.hpp>
+using namespace boost::mp11;
+
+// A simple metafunction that takes the first three items from a list
+template <typename T>
+using take3 = mp_take<T, mp_int<3>>;
+
+// Directly call take3
+static_assert(mp_same<
+    take3<mp_iota_c<9>>,
+    mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>>>::value, "");
+
+// Invoke a quoted take3 (mp_quote<take3>)
+static_assert(mp_same<
+    mp_invoke_q<mp_quote<take3>, mp_iota_c<9>>,
+    mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>>>::value, "");
+
+#if !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )
+
+// Invoke a composed take3 (mp_compose<take3>)
+static_assert(mp_same<
+    mp_invoke_q<mp_compose<take3>, mp_iota_c<9>>,
+    mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>>>::value, "");
+
+#endif
+
+// If we apply the following iteration, we expect to get all triplets of the list.
+using expected = mp_list<
+    mp_list<mp_size_t<0>, mp_size_t<1>, mp_size_t<2>>,
+    mp_list<mp_size_t<3>, mp_size_t<4>, mp_size_t<5>>,
+    mp_list<mp_size_t<6>, mp_size_t<7>, mp_size_t<8>>>;
+
+// First using mp_quote - this works as expected
+static_assert(
+    mp_same<
+        mp_iterate_q<
+            mp_iota_c<9>,
+            mp_quote<take3>,
+            mp_bind_back<mp_drop, mp_int<3>>>,
+        expected>::value, "");
+
+#if !BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, < 1900 )
+
+// Next, simply replace mp_quote with mp_compose.  We expect to get the same answer,
+// but we get a hard compiler error instead.
+static_assert(
+    mp_same<
+        mp_iterate_q<
+            mp_iota_c<9>,
+            mp_compose<take3>,
+            mp_bind_back<mp_drop, mp_int<3>>>,
+        expected>::value, "");
+
+#endif