Re: [GD-General] Eiffel

[Thatcher U. <tu...@tu...>]

On Dec 21, 2001 at 01:56 -0500, Kent Quirk wrote:
> 
> fact, one of the things that I love about Java and wish that C++ had was
> anonymous classes. They provide the only way to deal with the concept of
> functors in generic algorithms where the functor is defined at the same
> point as the algorithm is used. In C++ you can put it nearby. In Java
> you can stick an anonymous class right inline. It's a powerful, useful,
> and very general mechanism, similar to a lambda notation. 

Someone showed me this trick recently:

	...
	struct Function {
		static void Call(int arg) {
			// some code.
		}
	} Instance;
	SomeFunctionTakingAFunctionPointer(Function::Call);
	...

For extra flexibility, define an interface class:

struct Functor {
	virtual void Call(int arg);
};
void SomeFunctionTakingAFunctor(Functor* f);

	...
	struct HandleResults : public Functor {
		vector<int> results;
		void Call(int arg) { results.push_back(arg); }
	} Instance;
	// Call SomeFunction... and collect its results.
	SomeFunctionTakingAFunctor(&Instance);
	// Now Instance.results has the args passed to Instance.Call().

You can beef up HandleResults with a constructor and other members to
parameterize stuff.

I'm still sick of C++ though.  The useful modern stuff I want to use
is all a huge PITA.  Templates stink, (lack of) introspection stinks,
header files stink, manual memory management stinks, and pardon me,
but IMHO the STL stinks as far as usability goes.

-- 
Thatcher Ulrich <tu...@tu...>
http://tulrich.com