[lug] perl :)

[j davis]

so if syntax was changed to <3 then it would be ok...right?
jd

>From: rm at fabula.de
>Reply-To: lug at lug.boulder.co.us
>To: lug at lug.boulder.co.us
>Subject: Re: [lug] perl :)
>Date: Sun, 18 Aug 2002 21:28:11 +0200
>
>On Fri, Aug 16, 2002 at 09:31:00PM +0000, j davis wrote:
> >
> > it looks like i only need to change the operator and apperance number
> > to tweak this little tid-bit.
>
>No, the code below doesn't do what it's supposed to do.
>An item that exists three times in the source list will show
>up wrongly in the result list.
>
>  During the first occurence
>    ++$count{$_} == 2
>  will be wrong, hence the item won't make it throught the filter,
>  but the second time the item shows up
>    ++$count{$_} == 2
>  will be true and the item will be added to the result list.
>  When the item shows up the third time it won't pass, but that
>  doesn't matter, it's allready and wrongly in the result list.
>  One could write an @at_least_twice that way, but not the wanted
>  filter.
>
>    Ralf
>
> > jd
> >
> > >From: Rob Judd <rjudd at mlug.missouri.edu>
> > >Reply-To: lug at lug.boulder.co.us
> > >To: <lug at lug.boulder.co.us>
> > >Subject: Re: [lug] perl :)
> > >Date: Fri, 16 Aug 2002 10:05:51 -0600 (MDT)
> > >
> > >
> > >> you can't use this trick to find those that appear exactly twice or
> > >> thrice; it works for "first appearance" because you are dealing with
> > >> cardinal numbers, which can't go negative.
> > >>
> > >> to find elements that appeared a certain number of times, i'd 
>probably
> > >> do something like this:
> > >>
> > >>   my @appears_twice = do {
> > >>       my %count;
> > >>       foreach my $elt (@list) { ++$count{$_} }
> > >>       grep { $count{$_} == 2 };
> > >>   }
> > >
> > >Surely you can use something similar ... won't this work
> > >
> > >@twice = grep { ++$count{$_} == 2 } qw(a b a c d d e f g f h h);
> > >
> > >to give @twice = qw(a d f h) ?
> > >
> > >Cheers, Rob
> > >
> > >_______________________________________________
> > >Web Page:  http://lug.boulder.co.us
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> >
> >
> > thanks,
> > jd
> >
> > jd at taproot.bz
> > http://www.taproot.bz
> >
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thanks,
jd

jd at taproot.bz
http://www.taproot.bz

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