completed first revised draft of docs

example/features/free_function.cpp

@@ -0,0 +1,21 @@
+
+//[free_function
+#include <boost/contract.hpp>
+
+int inc(int& x) {
+    int result;
+    boost::shared_ptr<int const> old_x = BOOST_CONTRACT_OLDOF(x);
+    boost::contract::guard c = boost::contract::function()
+        .precondition([&] {
+            BOOST_CONTRACT_ASSERT(x < std::numberic_limits<int>::max());
+        })
+        .postcondition([&] {
+            BOOST_CONTRACT_ASSERT(x == *old_x + 1);
+            BOOST_CONTRACT_ASSERT(result == *old_x);
+        })
+    ;
+
+    return result = x++; // Function body.
+}
+//]
+