http://www.perlmonks.org?node_id=930522


in reply to Re: Array got modified!
in thread Array got modified!

O!! Thx man! This explains a lot. Never notice for yrs.
So I am gonna change my habit to do this way : 
@arr = qw/Foo Bar Blaz/;

foreach ( @arr ) {
  my $ele = $_;
  $ele =~ s/^(.)/x$1/;
}

# or this

while ( my $ele = <@arr> ) {
  $ele =~ s/^(.)/x$1/;
}

print "@arr"; # still 'Foo Bar Blaz'

[download]
Would you suggest which one is better, or any well suggested practice?

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Re^3: Array got modified!
by Jenda (Abbot) on Oct 10, 2011 at 10:25 UTC

    Could you explain, in your own words, what does the while ( my $ele = <@arr> ) { do?

    Once you do, go check the docs!

    It may seem to do what you seem to want if you are unlucky enough and the @arr doesn't contain anything interesting to the diamond operator, but even then it's horribly inefficient.

    Jenda
    Enoch was right!
    Enjoy the last years of Rome.

[reply]
[d/l]
      Hmm... my try is to take that array as a file handle to read, like @ARGV;

      I add up this code : 

      @x = qw/Foo Bar Blaz/;
#@x = qw//;

print "Before: @x$/";
while ( my $ele = <@x> ) {
 next unless $ele;
 print "$ele becomes ";
 $ele =~ s/^(.)/x$1/;
 print $ele . $/;
}
print "$/After: @x";
__END__

Then I have :
  Before: Foo Bar Blaz
  Foo becomes xFoo
  Bar becomes xBar
  Blaz becomes xBlaz

  After: Foo Bar Blaz

      [download]
      Is this work out properly by accident? This is what I want though...
      My observation is:
      if that's a empty array, it skips fine.
      And, without the diamond quote, it loops forever...
[reply]
[d/l]
        $ perl -MO=Deparse junk
print "Before: @x$/";
use File::Glob ();
while (defined(my $ele = glob(join $", @x))) {
    do {
        next unless $ele;
        print "$ele becomes ";
        $ele =~ s/^(.)/x$1/;
        print $ele . $/
    };
}
print "$/After: @x";
__DATA__
junk syntax OK

        [download]

        See glob, readline

[reply]
[d/l]
        Yes, it's working by accident (no spaces nor * in @x). For example: 
        perl -E '@arr=("a b",
    "c d",
    qw/e f g h a*/);
while (my $e = <@arr>) {
    say $e
}'

        [download]
        gives this output for me:
        a
b
c
d
e
f
g
h
address.txt
address.txt~
analytic
ascii.htm
aux-no-lex.lst

        [download]
[reply]
[d/l]
[select]
Re^3: Array got modified!
by BrowserUk (Patriarch) on Oct 10, 2011 at 03:36 UTC

    What is the point in editing $ele, if you then discard it?

[reply]
[d/l]
      haha.. sorry I mislead something... In general to say, I am not trying to edit the array, I just want to loop through and read the array

      By all means, I have to pick elements out, one by one, change to some expected pattern, then throw it to other subs to do something( which I didn't state in the code ).

      Also, it implies that, I will reuse the created array again, so that I don't want it changed.

[reply]
Re^3: Array got modified!
by choroba (Cardinal) on Oct 10, 2011 at 07:31 UTC
    Never mind, I did not read the post properly.
[reply]

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