>
> The Very Big Advantage (Tm), is that you get syntax checking, while still
> using a type diversely. That's impossible to do (at compile-time) without
> generics.
>
> Probably the best example of this is something like TList:
>
> Without generics:
>
> TOrange = class ... end;
> TApple = class ... end;
>
> var
> T: TList;
> begin
> T := TList.Create();
> T.Add(TApple.Create());
> T.Add(TOrange.Create());
> // Whoops, what was that? Now our program might crash.
> end;
>
> Of course, we could create a specialized TAppleList that only accepts Apples,
> but that's boring and hard work. A much cleaner way is generics:
>
> var
> T: TList<TApple>;
> begin
> T := TList<TApple>.Create();
> T.Add(TApple.Create());
> T.Add(TOrange.Create());
> // This wont compile! The problem is prevented at compile-time!
> end;
>
> I hope that answers your question as to why it's a good idea :-)
>
> --
> Regards,
> Christian Iversen
Sort of, but I don't see why people use TApple and TOrange examples all the
time ;-) I mean
when was the last time you actually programmed a software application that was
organizing
Apples and Oranges? I use things like strings, databases, integers, FTP, CGI,
stringlists,
etc. Sure apples and oranges can represent a sort of metaphor for ANYTHING, but
I'd prefer
just to cut straight to the real world example instead.
I guess the real world examples are hard to display unless you have actually
used generics
in a software program, and you are willing to offer code snippets from the
program.
I wish for example, I could see someone using something more real world such as:
-----BEGIN OF CASE STUDY-----
(just a fake one)
---Description---
I used generics in my FTP uploader software application and it prevented
an error for me.
---Code examples---
Here are some code examples taken right from my real world ftp
application written in C++. Since Pascal doesn't have generics currently,
this example is in C++ only to help you see why they are useful in an
existing software application.
..............
......insert code here ....
..............
---Conclusion---
My executable size is now 1400KB whereas before when not using
generics it was 1340KB. The 60KB gain was not a big deal. My
conclusion is that generics offer significant advantages, but they
shouldn't be used in some situations.
If Pascal implements generics I estimate my executable will be about
1400KB too, and the syntax will be as follows if I was to convert
my C++ application to Pascal using generics:
......
...insert code here...
.....
---Other notes:---
Generics don't work well in the following situations:
A)....using a type diversely can cause issues when... ....
B).....abusing generics could cause issues if you if... ...
C).....generally they shouldn't be used if.... ...
-----END OF CASE STUDY-----
However, I suppose I'm idealistic and too much of a real world guy some times.
Case studies
can be perfect if you have software program already in existence, or if you can
create a
small demo program that is fully functional and actually does something real on
the
computer. I helps more easily prove the advantages of a certain programming.
paradigm. Then
there are video case studies, but I won't get in to those since those are more
to do with
demonstrating visual advantages of GUI's and software features.
_______________________________________________
fpc-devel maillist - fpc-devel@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-devel
