HOP file iterator

ady has asked for the wisdom of the Perl Monks concerning the following question:

Brother monks!

I'm stuck in a simple code snippet from HOP (4.3.3), can't quite understand why this spits out *all* lines from the file (<DATA>) and not just the first 2 lines.

Seems the first NEXTVAL($it) slurps the *whole* file instead of just reading one line up to \n, but why is that so?

Any pointers much appreciated!

#!/usr/bin/perl -w
use strict;
use warnings;

sub NEXTVAL { $_[0]->() }

sub Iterator (&) { return $_[0] }

sub filehandle_iterator {
  my $fh = shift;
  return Iterator { <$fh> };
}

my $it = filehandle_iterator(*DATA);
for (1..2) { print NEXTVAL($it); }

__END__
line 1
line 2
line 3
line 4
line 5
[download]

Best Regards,
Allan Dystrup

Comment on HOP file iterator Download Code

Replies are listed 'Best First'.
Re: HOP file iterator by BrowserUk (Patriarch) on Mar 26, 2006 at 16:22 UTC
In a word, context. Try: `for (1..2) { print scalar NEXTVAL($it); }` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal? "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re^2: HOP file iterator by ady (Deacon) on Mar 26, 2006 at 16:32 UTC
<blush> yes, Because print takes a LIST, anything in the LIST is evaluated in list context, and any subroutine that you call will have one or more of its expressions evaluated in list context Thanks BrowserUk! allan	[reply]
Re: HOP file iterator by blogical (Pilgrim) on Mar 26, 2006 at 16:24 UTC
Do you perchance mean `sub NEXTVAL { $_[0]->($_[1])` [download] ? "One is enough. If you are acquainted with the principle, what do you care for the myriad instances and applications?" - Henry David Thoreau, Walden	[reply] [d/l]


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