U++ forum: Welcome to the forum

Re: Anonymous delegates [message #13030 is a reply to message #13019]

Wed, 05 December 2007 21:33

Zardos
Messages: 62
Registered: April 2007

Member

luzr wrote on Wed, 05 December 2007 15:33

Zardos wrote on Wed, 07 November 2007 21:17

If you use it, please be aware it's still only a macro.

To illustrate the fundamentel problem a simple example:

Vector<int> CreateResultVector() {
   Vector<int> r;
   r.Add(1);
   r.Add(2);
   r.Add(3);
   return r;
}

...

foreach(int e, CreateResultVector())
   DUMP(e);

Basically the code is stupidly translated to something like this:

for(int i = 0; i < CreateResultVector().GetCount(); i++)
   DUMP(CreateResultVector()[i]);

... CreateResultVector is called multiple times!
But this is probably not what you would expect from a real foreach build into the language!

Curiously, this is exactly what I would expect... (I mean, called multiple times).

Mirek

Yes, but you are a very experienced c++ programmer. You know "foreach" is a macro and simply expect "macro behaviour".

If a "foreach" would be available in c++ it would probably evaluate CreateResultVector only once like in C#, Python or Ruby.

For example the following ruby code evaluates create_result_vector only once:

def create_result_vector
	[1, 2, 3]
end

for e in create_result_vector do
	puts e
end

- Ralf

Report message to a moderator