use of uninitialized values

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

I have the following in my script -

$coord_{$key1}{$key2}[[2]] = $sth->fetchrow_array;
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where fetchrow_array belongs to DBI

Sometimes though fetchrow_array will not find an entry, so what I want to do is store missing entries in my database as 0 in the corresponding variable. So lets say the corresponding entry for $coord_{"AB"}{5}[[2]] has no entry in the database, then I want $coord_{"AB"}{5}[[2]] = 0 instead of $coord_{"AB"}{5}[[2]] = "uninitialized value";

So I could use something like -

if($coord_{$key1}{$key2}[2] eq "uninitialized value")
{
  $coord_{$key1}{$key2}[2] = 0;
}
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but how does perl represent this "uninitialized value" that I'm using above? I hope that makes sense.

Thanks
Barry.

Comment on use of uninitialized values Select or Download Code

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Re: use of uninitialized values
by nothingmuch (Priest) on Apr 06, 2003 at 14:13 UTC

undef

undef @bar

$foo = undef

defined

if(not defined($coord_{$key1}{$key2}[2]))
 {
   $coord_{$key1}{$key2}[2] = 0;
 }
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$coord_{$key1}{$key2}[2] = 0 unless defined $coord_{$key1}{$key2}[2];
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$coord_{$key1}{$key2}[2] ||= 0;
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Update:

undef

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Re: use of uninitialized values
by Anonymous Monk on Apr 06, 2003 at 14:13 UTC

$coord_{$key1}{$key2}[2] ||= 0;

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Re: use of uninitialized values
by graff (Chancellor) on Apr 07, 2003 at 01:08 UTC

select NVL(some_column,0) from some_table where some_condition...
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Re: Re: use of uninitialized values

by pfaut (Priest) on Apr 07, 2003 at 03:39 UTC

PostgreSQL and SQL Server use COALESCE. You can give COALESCE a list of values. It will return the first one that is not NULL.

90% of every Perl application is already written. ⇒

dragonchild

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