Algorithms: Introduce helper Utils::equal

Takes a member (function) pointer and a value and returns a functor,
that takes a instance of the mfp's class and returns whether it's equal
to value. Sounds complicated, but is a common pattern that is easy to
understand.

Change-Id: Iaaeb90488d34ddfd6940dadd4c66705381198fee
Reviewed-by: Nikita Baryshnikov <nib952051@gmail.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/libs/utils/algorithm.h

@@ -121,6 +121,23 @@ typename T::value_type findOrDefault(const T &container, F function)
     return findOr(container, typename T::value_type(), function);
 }
 
+//////////////////
+// find helpers
+//////////////////
+template<typename R, typename S, typename T>
+auto equal(R (S::*function)() const, T value)
+    -> decltype(std::bind<bool>(std::equal_to<T>(), value, std::bind(function, std::placeholders::_1)))
+{
+    return std::bind<bool>(std::equal_to<T>(), value, std::bind(function, std::placeholders::_1));
+}
+
+template<typename R, typename S, typename T>
+auto equal(R (S::*member), T value)
+    -> decltype(std::bind<bool>(std::equal_to<T>(), value, std::bind(member, std::placeholders::_1)))
+{
+    return std::bind<bool>(std::equal_to<T>(), value, std::bind(member, std::placeholders::_1));
+}
+
 //////////////////
 // transform
 /////////////////