2009/3/17 Jay Savage <daggerqu...@gmail.com>:
> On Tue, Mar 17, 2009 at 8:16 AM, Dermot <paik...@googlemail.com> wrote:
>> Hi All,
>>
>> I am unsure if the following statement is going to do what I want.
>>
>> I want to test if there is a value in $hash_ref{'someval'} NOT if the
>> key is defined. I'd also like to avoid un-sightly "undefined value"
>> errors.
>
>
> Hi Dermot,
>
> It really depends on what the expected/legal values are.
>
> For numeric values, a simple 'if $x{x}' will normally suffice. The
> exception is in the case that zero is a legal value, in which case you
> need 'defined.' The perldoc exists for a nice rundown.
>
> If there are additional constraints, you really need at least two
> tests. Simply testing truth or definiedness will not tell you if the
> value is in range, and simply testing the value will throw an error if
> the element isn't defined, e.g.
>
> if ( $x{x} and $x{x} =~ /\w+/ ) {}
> if ( defined $x{x} and $x{x} > -4 ) {} # 0 is in range, so we
> need 'defined'
>
Thanx for the replies. I have opted for the defined option as I think
it makes the code fragment's intention clearer but just to confirm
if ($x{$x}) inspects the key's value, not simply the existence of a key?
Dp.
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