result_of implementation that makes use of C++0x decltype, from Daniel Walker. Fixes #862.

[SVN r45256]

utility.htm

@@ -152,11 +152,13 @@ void f() {
                 ...,t<em>N</em>)</code>. The implementation permits
                 the type <code>F</code> to be a function pointer,
                 function reference, member function pointer, or class
-                type. When <code>F</code> is a class type with a
-                member type <code>result_type</code>,
+                type.</p> <p>If your compiler does not support
+                <code>decltype</code>, then when <code>F</code> is a
+                class type with a member type <code>result_type</code>,
                 <code>result_of&lt;F(T1, T2, ...,
                 T<em>N</em>)&gt;</code> is
-                <code>F::result_type</code>. Otherwise,
+                <code>F::result_type</code>. When <code>F</code>
+                does not contain <code>result_type</code>, 
                 <code>result_of&lt;F(T1, T2, ...,
                 T<em>N</em>)&gt;</code> is <code>F::result&lt;F(T1,
                 T2, ..., T<em>N</em>)&gt;::type</code> when