uninitialized value in numeric eq (==)

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

Dear Monks,

I have this error message:

Use of uninitialized value in numeric eq (==) at Creating_table_D.pl l
+ine 31.
Use of uninitialized value in numeric eq (==) at Creating_table_D.pl l
+ine 35.
[download]

for the following offending code:


sub create_table ($) {

  my($schema_in) = $_;

  if ($schema_in == "1"){ # offending line 1
    my @tables = qw/A/;
  }

  if ($schema_in == "2"){# offending line 2
    my @tables = qw/A B C/;
  }
[download]

I have tried a number of variations on a theme. Does anyone have a quick explanation?

Comment on uninitialized value in numeric eq (==) Select or Download Code

Replies are listed 'Best First'.
Re: uninitialized value in numeric eq (==) by edan (Curate) on Nov 11, 2003 at 11:46 UTC
Try changing: `sub create_table ($) { my($schema_in) = $_;` [download] to: `sub create_table { my ($schema_in) = @_;` [download] See if that helps. Read perlvar for more info on the difference between `$_` and `@_` (they are very different, even though they look similar) -- 3dan	[reply] [d/l] [select]
Re: uninitialized value in numeric eq (==) by Roger (Parson) on Nov 11, 2003 at 11:53 UTC
You can either change your code - `my($schema_in) = $_;` [download] to this - `my($schema_in) = @_;` [download] or this - `my $schema_in = shift;` [download]	[reply] [d/l] [select]
Re: uninitialized value in numeric eq (==) by rdfield (Priest) on Nov 11, 2003 at 11:45 UTC
Why put quotes around the numbers 1 and 2? Why use a prototype? have you checked the value of `$schema_in`? rdfield	[reply] [d/l]
Re: Re: uninitialized value in numeric eq (==) by hmerrill (Friar) on Nov 11, 2003 at 13:37 UTC
rdfield is right on the money. Pay attention to exactly what error message are trying to tell you - they are usually pretty easy to understand if you take a minute and really look at it. Notice `Use of uninitialized value in numeric eq (==) at Creating_table_D.pl line 31. Use of uninitialized value in numeric eq (==) at Creating_table_D.pl line 35.` [download] Here's your code: `sub create_table ($) { my($schema_in) = $_; if ($schema_in == "1"){ # offending line 1 my @tables = qw/A/; } if ($schema_in == "2"){# offending line 2 my @tables = qw/A B C/; }` [download] Notice in particular Use of uninitialized value. This probably means that $schema_in has *NO* value. As rdfield suggested, do some debugging - print out the value of $schema_in in subroutine 'create_table' to see if it is receiving the value you think it's receiving. Notice another thing - when doing a numeric comparison, you don't want to test using string "1" - you want to test using number 1 - without quotes around it. If you include the quotes and $schema_in contains a number, then perl will have to convert the string to a number and then do the numeric comparison. HTH.	[reply] [d/l] [select]
Re: uninitialized value in numeric eq (==) by EvdB (Deacon) on Nov 11, 2003 at 11:50 UTC
Change `my($schema_in) = $_;` into `my $schema_in = shift;` and it works. `$_` is not set on enty into sub routine, `@_` is. --`tidiness is the memory loss of environmental mnemonics`	[reply] [d/l] [select]