Re: intro

At 11:25 PM 10/29/99 -0400, John Porter wrote:
>Peter Scott wrote:
> >
> > I don't
> > even mention dynamic variables until the object-oriented class I'm
> > currently designing for a day 4, when it's kinda unavoidable :-)
>
>Huh?  I write plenty of OO code, and I find the need for global
>vars very rare.  But what, IMHO, *is* unavoidable is the occasional
>need to
>
>         local $/ = '';
>
>         local $" = ', ';
>
>         local $^W;
>
>         local $_;  # for some loops
>
>and so on.  This is what makes globals truly unavoidable.

I don't mention those.  In 3 days starting from scratch one has to leave 
some things out, and I find I can leave those things out.  There are other 
ways for people to read a whole file into a string and insert commas 
between list items, and anyone who wants to selectively disable warnings or 
save $_ probably can find out how without my having to perplex a whole 
class with the quagmire of package variables, especially magic ones.

On the other hand, teaching OO is the first time I mention packages, and 
the concept would be somewhat flat without demonstrating how namespaces 
separate variables.  Can't do that with lexicals.  Even though I then go on 
to demonstrate how good OO code doesn't use said variables, the notion of a 
package needs concrete, easy-to-understand illustrations.

Some things have to be approached obliquely.  Clearly, use fields and 
pseudo-hashes are the way to construct instance data, but that's just not 
the way to start out teaching OO Perl, IMHO.  So I get at it the 
old-fashioned way first.  Sort of the pedagogical equivalent of phylogeny 
recapitulating ontogeny...

Of course, TIMTOWTTI...


--
Peter Scott
Pacific Systems Design Technologies