Delegates tutorial meeting specific criteria?

[sherifffruitfly]

I'm looking for a tutorial/sample specifically aimed at showing why
life is better with them than without them. Ideally, what I'd like to
see in the tutorial I'm looking for:

1) No discussion of events.
2) The "non delegates way" and "the delegates way" of dealing with a
problem both presented.
3) A clear explanation of why "the delegates way" is either clearer,
more robust, or more easily maintainable/extensible.
4) One other thing which I'm forgetting atm. :)


I've googled lots, and haven't found even a good approximation to what
I'm looking for.

Thanks for any suggestions!

[sherifffruitfly]

Re: Delegates tutorial meeting specific criteria?

On Feb 11, 6:56 pm, Jesse McGrew <jmcg...@gmail. comwrote:

Here's one example: a map function.

Thanks Jesse - that's the kind of thing I'm looking for - I'll study
the example.

Also makes me think of Mathematica - your "Map" looks suspiciously
similar in concept to theirs - I'll check theirs out and see if any
inspiration is to be had.

Thanks again!

[Jesse McGrew]

Re: Delegates tutorial meeting specific criteria?

On Feb 11, 7:27 pm, sherifffruitfly <sherifffruit.. .@gmail.comwrot e:

On Feb 11, 6:56 pm, Jesse McGrew <jmcg...@gmail. comwrote:
>

Here's one example: a map function.

>
Thanks Jesse - that's the kind of thing I'm looking for - I'll study
the example.
>
Also makes me think of Mathematica - your "Map" looks suspiciously
similar in concept to theirs - I'll check theirs out and see if any
inspiration is to be had.

Yeah, it's a common concept. In fact, .NET already includes the method
Array.ConvertAl l, which does exactly the same thing.

Some of the other static methods on Array are also good examples of
what delegates are good for: see Exists, Find, TrueForAll, etc. where
you supply a delegate to select the elements you care about.

Jesse

[Marc Gravell]

Re: Delegates tutorial meeting specific criteria?

I'm looking for a tutorial/sample specifically aimed at showing why

life is better with them than without them. Ideally, what I'd like to
see in the tutorial I'm looking for:

How about LINQ? (in particular, LINQ-to-objects). The following uses
lambda notation, but (in this context) this is just a delegate:

var query = source.Where(x =x.Bar == bar)
.GroupBy(x =x.Category).Se lect(y =new
{
Name = y.Key,
Total = y.Sum(z =z.Bloop),
Count = y.Count()
});

which is identical to the alternative syntax:

var query2 = from x in source
where x.Bar == bar
group x by x.Category into y
select new
{
Name = y.Key,
Total = y.Sum(z =z.Bloop),
Count = y.Count()
};

This (both: they are identical) is doing a filter with a predicate
(via a delegate), grouping by a selection (via a delegate), and
performing a projection (via a delegate). To do that without delegates
(or expressions) requires looping, running your own filter, worrying
about the dictionary, performing the aggregation etc.

But even better: with this approach, we can swap the filter at runtime
- i.e. if we used:

Func<Foo, boolfilter;
switch(somethin g) {
case [etc]:
filter = whatever;
break;
...
}

We could then use [etc].Where(filter).[etc], and we have a runtime
filter. Very easy and extensible.

Marc