Re: uninitialized variables

IF (and ONLY if) you can handle a default value ok, you could do something like this:
while(<>) { my ($x, $y, $z) = (0,0,0); ($x, $y, $z)=split; # do whatever }
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Or you could get silly, and do something like:

while(<>) {
    my @flds=split;
    my ($x, $y, $z)=(@flds,0,0,0);

    # do whatever
}
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But then you have to be ready to handle 0's (or whatever other default you chose) when data is missing, and you have to make sure you don't pick a default value that could be real data.

It's much safer to use defined and know when your fields are missing; that way you get something like real NULL handling, in the SQL sense.
--
Mike

Edit: thanks to ariels for the correction!

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Re: Re: uninitialized variables by ariels (Curate) on Mar 28, 2002 at 17:29 UTC
There's a subtle difference between the 2 forms you suggest: only the second works! When you say `my ($x, $y, $z) = (0,0,0); ($x, $y, $z)=split;` [download] you always set `$x`, `$y` and `$z`! That's what assignment is all about! Here it is in the debugger: main::(-e:1): 0 DB<1> ($x,$y,$z)=(2,3,4) DB<2> ($x,$y,$z)=split ' ',"two words" DB<3> x $x 0 'two' DB<4> x $y 0 'words' DB<5> x $z 0 undef The second works, because it isn't trying to reassign `undef`.	[reply] [d/l] [select]

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Re: Re: uninitialized variables
by ariels (Curate) on Mar 28, 2002 at 17:29 UTC

There's a subtle difference between the 2 forms you suggest: only the second works!

When you say

my ($x, $y, $z) = (0,0,0);
($x, $y, $z)=split;
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always

$x

$y

$z

Here it is in the debugger:

main::(-e:1):   0
  DB<1> ($x,$y,$z)=(2,3,4)

  DB<2> ($x,$y,$z)=split ' ',"two words"

  DB<3> x $x
0  'two'
  DB<4> x $y
0  'words'
  DB<5> x $z
0  undef

The second works, because it isn't trying to reassign undef.

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