Added SelectArg and MemFunSelectArg*

The MemFunSelectArg* functions can be used to select
a specific argument from a signal. For example this would
select the string argument as argument to the callback:

Signal<void, int, float, string> signal;
signal.connect(MemFunSelectArg2(obj, &Object::takesOneStringArg));
signal.emit(10, 3.14, "hello");

...

void Object::takesOneStringArg(const string& value) {
...
}

1 files changed, 19 insertions, 0 deletions

diff --git a/src/FbTk/STLUtil.hh b/src/FbTk/STLUtil.hh
index d427a17..e08036a 100644
--- a/src/FbTk/STLUtil.hh
+++ b/src/FbTk/STLUtil.hh
@@ -26,6 +26,25 @@
 namespace FbTk {
 namespace STLUtil {
 
+template<bool C, typename Ta, typename Tb>
+struct IfThenElse;
+
+template<typename Ta, typename Tb>
+struct IfThenElse<true, Ta, Tb> {
+    Ta& operator ()(Ta& ta, Tb& tb) const {
+        return ta;
+    }
+    typedef Ta ResultType;
+};
+
+template<typename Ta, typename Tb>
+struct IfThenElse<false, Ta, Tb> {
+    Tb& operator ()(Ta& ta, Tb& tb) const {
+        return tb;
+    }
+    typedef Tb ResultType;
+};
+
 /// calls delete on each item in the container and then clears the container
 template <typename A>
 void destroyAndClear(A &a) {