in reply to chomp any data structure recursively

Yours is bugged. It looks at the outer $_ in all those ref calls. Just happens to work.

Here's a non-recursive version: 

sub mychomp {
  while (@_) {
    eval { chomp $_[0] }, shift, next unless ref;
    (push @_, @{shift @_}), next if ref $_[0] eq 'ARRAY';
    (push @_, values %{shift @_}), next if ref $_[0] eq 'HASH';
    shift;
  }
}

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-- Randal L. Schwartz, Perl hacker

update: I didn't claim it was a working version. Thanks for the updates in the thread. {grin}

Also, I didn't see the unusual multi-line backwards-for in the original code, so it appears to be less buggy than I thought. {sigh}

Replies are listed 'Best First'.
Re: Re: chomp any data structure recursively
by runrig (Abbot) on Dec 21, 2001 at 01:51 UTC
    I think your version is butchering array references, and it doesn't handle scalar references. I think this works:
    sub mychomp {
  while (@_) {
    for (shift) {
      ref or (eval { chomp if defined }, last);
      ref eq 'SCALAR' and (eval { chomp $$_ if defined $$_ }, last);
      ref eq 'ARRAY'  and (do { push @_, map \$_, @$_ },  last);
      ref eq 'HASH'   and (do { push @_, map \$_, values %$_ }, last);
    }
  }
}

    [download]
    Question, though, why are we eval'ing the scalar chomps? chomp warns on undef, but does it fail under some condition? (update: I think I answered my own question...its for constant values which can't be chomped).
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[d/l]
Re: Re: chomp any data structure recursively
by Anonymous Monk on Dec 21, 2001 at 01:50 UTC
    Errr, yours just happens not to work. 
    use Data::Dumper;
sub mychomp {
  while (@_) {
    eval {chomp $_[0] }, shift, next unless ref ;
    (push @_, @{shift @_}), next if ref $_[0] eq 'ARRAY';
    (push @_, values %{shift @_}), next if ref $_[0] eq 'HASH';
    shift;
  }
}

my $foo = "scalar\n";
my @foo = (
  [
      "bar\n", "foo\n", "xyzzy\n",
      { blaat => "hee hee\n", hihi => "hoho\n" }
  ],
  {qw(a b c d e f)}, "w00t\n", \$foo, \ "read-only\n"
);
mychomp(@foo);
print Dumper(\@foo);
__END__


$VAR1 = [
          'ARRAY(0x80f3764)',
          'HASH(0x81495a8)',
          'w00t',
          'SCALAR(0x8131fe8)',
          'SCALAR(0x813e78c)'
        ];

    [download]
[reply]
[d/l]
Re: Re: chomp any data structure recursively
by Juerd (Abbot) on Dec 21, 2001 at 01:41 UTC
    Which $_ is the outer one?
    The refs should see the values of @_. I can't think of a reason why they wouldn't (help me out here :)

    In short, this is the pseudocode: 
    sub mychomp {
    for (@_){
           $_ is iterable && mychomp it
        || $_ is a scalar ref && try to chomp its scalar
        || $_ is not any other reference && chomp it
    }
}

    [download]
    I'd be quite surprised my code works with many different structures if it's bugged.

    Could you please give an example of what could go wrong? (of course accompanied by an explanation :)

    Anyway, thanks for pointing out that it's bugged.

    2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$

    [download]

[reply]
[d/l]
[select]
      Looking at just this part: 
      sub mychomp { 
          ref eq 'ARRAY' ...

      [download]
      That's ref of $_, which you have not yet set up, so it's the outer $_ from the caller. Luckily, you didn't test your subroutine with something that needed ref-ARRAY treatment as an argument. {grin}.

      -- Randal L. Schwartz, Perl hacker

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[d/l]
        I always thought and assumed the for modifier would set $_ ...
        (You did see it, didn't you? It's just before the sub's closing curly.) 

        2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$

        [download]

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[d/l]
Re: Re: chomp any data structure recursively
by Anonymous Monk on Dec 21, 2001 at 02:35 UTC

    I tracked this thread for a while. merlyn incorrectly calls posted code buggy and supplies replacement code that is buggy and his node gets voted to +6. He doesn't update his node to acknowledge either mistake when it is pointed out and his node still climbs 3 more points to +9 after both errors were pointed out in followups. Now that's what I call personality voting!

[reply]
      Well, then, he doesn't deserve a best node of the day award for this one, but to be fair, he did acknowlege one (update: now both) of his mistakes, and all I did was take his idea and "fix" it (update: and gbarr just blew mine away :), so although it was buggy starting out, it was an interesting idea to begin with, and I don't begrudge him a few XP for that (as if I cared seriously about XP at all)...

      If someone posts a "you blew it" reply, I'd expect a followup "Hey, you're right" and maybe a fix (depending on time available -- many of us are busy, you know), but if someone (e.g., me) posts a fix, then what's the point in replying to that, especially if you're busy?

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