add 'is_placeholder' test

[SVN r16450]

test/is_placeholder.cpp

@@ -0,0 +1,48 @@
+//-----------------------------------------------------------------------------
+// boost mpl/test/is_placeholder.cpp source file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2000-02
+// Aleksey Gurtovoy
+//
+// Permission to use, copy, modify, distribute and sell this software
+// and its documentation for any purpose is hereby granted without fee, 
+// provided that the above copyright notice appears in all copies and 
+// that both the copyright notice and this permission notice appear in 
+// supporting documentation. No representations are made about the 
+// suitability of this software for any purpose. It is provided "as is" 
+// without express or implied warranty.
+
+#include "boost/mpl/is_placeholder.hpp"
+#include "boost/mpl/placeholder.hpp"
+
+#include "boost/preprocessor/repeat.hpp"
+#include "boost/preprocessor/inc.hpp"
+#include "boost/preprocessor/cat.hpp"
+#include "boost/static_assert.hpp"
+
+using namespace boost::mpl;
+
+struct UDT;
+    
+#define AUX_IS_PLACEHOLDER_TEST(unused1, n, unused2) \
+    { BOOST_STATIC_ASSERT(is_placeholder< \
+          BOOST_PP_CAT(_,BOOST_PP_INC(n)) \
+        >::value); } \
+/**/
+
+int main()
+{
+    BOOST_STATIC_ASSERT(!is_placeholder<int>::value);
+    BOOST_STATIC_ASSERT(!is_placeholder<UDT>::value);
+    BOOST_STATIC_ASSERT(is_placeholder<_>::value);
+    
+    BOOST_PP_REPEAT(
+          BOOST_MPL_METAFUNCTION_MAX_ARITY
+        , AUX_IS_PLACEHOLDER_TEST
+        , unused
+        )
+        
+    return 0;
+}