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HTTP/2 200 cache-control: max-age=43200 server: Combust/Plack (Perl) vary: Accept-Encoding content-encoding: gzip content-length: 2745 content-type: text/html; charset=utf-8 last-modified: Sat, 11 Oct 2025 15:45:31 GMT traceparent: f4aa8c57d87a5429b2ed38df6d71fca9 strict-transport-security: max-age=15768000 Diamond iteration (was: Fighting the Good Fight against spam deluge) - nntp.perl.org

Front page | perl.perl5.porters | Postings from August 2008

Diamond iteration (was: Fighting the Good Fight against spam deluge)

From:

Tom Christiansen

Date:

August 1, 2008 08:27

Subject:

Diamond iteration (was: Fighting the Good Fight against spam deluge)

Message ID:

32336.1217604417@chthon

In-Reply-To: Message from jvromans@squirrel.nl (Johan Vromans) 
   of "Fri, 01 Aug 2008 12:28:49 +0200." <18578.58721.180685.719191@phoenix.squirrel.nl> 
> [Quoting Tom Christiansen, on July 31 2008, 16:15, in "Fighting the Good Fi"]
>> In-Reply-To: Message from Johan Vromans <jvromans@squirrel.nl> 
>>>  I'd go for a nice iterator class instead of <<<<>>>> weirdness.
>> But now I'm curious--a condition for which, per Dorothy Parker, there
>> is no cure :).  Still, I'll try to cure it by asking whether you
>> might you mean:
>> (1) A class that has some sort of:
>> 
>>     use overload "<>" => sub { ... };
> Basically, yes.
Good!
> =head1 NAME
> Iterator::Diamond - Iterate through the files from ARGV
> =head1 VERSION
(and so and so forth)
Gosh, Johan, you're ahead of the game!  With the doc/spec all complete and
written out nicely like that, that makes it what, like 90% done?  (and only
90% to go, I know, I know. :-)
Does it iterate per glob, too? ;-}
I really need to break myself from using 
    open(SETUP, <~joeblow/.exrc>)
at least, or maybe even also 
    # DON'T NEED: chdir <~joeblow> || grump();
    while ($dot_his = <~joeblow/.??*>) {  # CUZ gets full pathname
	next unless -f -r -T $dot_his;  # no, no -A :-)
	open(SETUP, "< $dot_his\0") || grump();  
	...
    } 
but it's just so danged convenient.  The problem was that last I looked,
you have to finish the iteration yourself (as in example #2 with the
while), or else there'll be a dangling dirhandle left unclosed and
consuming system resources: one of your process's FDs--and also thus 
one out of the syswide UFD table in the kernel, too.
I know: old perl hackers, like old nuns, have strange old habits.
I do think (but don't quote me; quote him if you can) that Larry 
likes the angle-operator (as he calls it) to be an iterator, or 
rather *the* iterator, and that classes that co-opt it for their 
own iteration strategies are cool.  That makes your idea cool.
I still yearn for <> to work on DHs opened by opendir, too.
Never saw why it didn't.
    $his_dir = <~joeblow>;  # XXX: just lost an FD
    opendir(DH, $his_dir) || grump();
    ### chdir($his_dir) || grump();
    ### "I hate programs that chdir" --Boyd Roberts
    while (<DH>) {
	next unless /^\./;
	next unless -f -r -T;  # WRONG: now needs $his_dir!
	open(SETUP, "< $his_dir/$_\0") || grump();  
	....
    } 
--tom