[boost] [signals] Minor patch suggestion for last_value.hpp

From: Ames Andreas (Andreas.Ames_at_[hidden])
Date: 2005-09-26 12:29:05

Hello all,

I have the problem that signal's default combiner last_value is OOTB
only usable with non-empty signals, unless the return type is void.

The attached patch tries to circumvent this by returning an
optional<T> instead of a T.

cheers,

aa

-- 
Andreas Ames | Programmer | Comergo GmbH |
Voice:  [phone] | andreas . ames AT comergo . com

Index: boost/boost/last_value.hpp
===================================================================
RCS file: /cc/CVSGlobal/tools/extern/boost/boost/last_value.hpp,v
retrieving revision 1.1.1.1
diff -u -r1.1.1.1 last_value.hpp
--- last_value.hpp	2005/08/09 03:52:52	1.1.1.1
+++ last_value.hpp	2005/09/26 17:22:32
@@ -12,16 +12,17 @@
 
 #include <cassert>
 
+#include <boost/optional.hpp>
+
 namespace boost {
   template<typename T>
   struct last_value {
-    typedef T result_type;
+    typedef optional<T> result_type;
 
     template<typename InputIterator>
-    T operator()(InputIterator first, InputIterator last) const
+    optional<T> operator()(InputIterator first, InputIterator last) const
     {
-      assert(first != last);
-      T value = *first++;
+      optional<T> value;
       while (first != last)
         value = *first++;
       return value;