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

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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

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