Add helper function for maps.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/util/map.h

@@ -0,0 +1,22 @@
+/*
+Copyright (c) 2013 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#pragma once
+#include <unordered_map>
+
+namespace lean {
+/**
+   \brief Helper function for inserting k->v into the map \c m.
+*/
+template<typename M>
+void insert(M & m, typename M::key_type const & k, typename M::mapped_type const & v) {
+    auto p = m.insert(std::make_pair(k, v));
+    if (!p.second) {
+        // m already contains an entry with key \c k.
+        p.first->second = v;
+    }
+}
+}