add boost on mac

macx64/include/boost/metaparse/v1/cpp11/impl/string_at.hpp

@@ -0,0 +1,41 @@
+#ifndef BOOST_METAPARSE_V1_CPP11_IMPL_STRING_AT_HPP
+#define BOOST_METAPARSE_V1_CPP11_IMPL_STRING_AT_HPP
+
+// Copyright Abel Sinkovics (abel@sinkovics.hu)  2016.
+// 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/metaparse/v1/impl/no_char.hpp>
+
+#include <boost/metaparse/limit_string_size.hpp>
+
+namespace boost
+{
+  namespace metaparse
+  {
+    namespace v1
+    {
+      namespace impl
+      {
+        template <int MaxLen, int Len, class T>
+        constexpr int string_at(const T (&s)[Len], int n)
+        {
+          // "MaxLen + 1" adds the \0 character of the string literal to the
+          // limit
+          static_assert(Len <= MaxLen + 1, "String literal is too long.");
+          return n >= Len - 1 ? BOOST_NO_CHAR : s[n];
+        }
+      }
+    }
+  }
+}
+
+#ifdef BOOST_METAPARSE_V1_STRING_AT
+#  error BOOST_METAPARSE_V1_STRING_AT already defined
+#endif
+#define BOOST_METAPARSE_V1_STRING_AT \
+  ::boost::metaparse::v1::impl::string_at<BOOST_METAPARSE_LIMIT_STRING_SIZE>
+
+#endif
+