in reply to Re: Truthfulness of references
in thread Truthfulness of references

Thanks GrandFather. That's what I thought the test was actually doing

So what's a good way to test for truth here?
The reason for the post is that I've written a few subroutines that either return a reference to a complex data structure OR filter entries out of the previously created data structure. The problem I noticed was that if I ended up filtering out all of the entries and returning a reference to the filtered data structure, my test for truth returned unexpected results ( ie: it returned true eventhough the data structure was empty.

3 follow up questions:
1. Should I be returning references from these types of sub-routines?
2. If so, what's the best way to return them?
3. What's a good way to test for truthfulness: 

if ( %$ref ) {
 ...do something
}

[download]

or... 

if ( %$ref && ref $ref eq 'HASH' ) {
 ...do something
}

[download]

Thanks again for your help.
njcodewarrior

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Re^3: Truthfulness of references
by Anno (Deacon) on Mar 13, 2007 at 13:11 UTC
    You wrote:

    3. What's a good way to test for truthfulness:

    "Truthfulness" is an unusual term for the boolean value of something. "Truth value" is more common. 

    if ( %$ref ) {
 ...do something
}

    [download]
    That code is fine if you know that $ref holds a hash ref and you need to decide whether the hash is empty.

    or... 

    if ( %$ref && ref $ref eq 'HASH' ) {
 ...do something
}

    [download]
     Here, it seems, you want to check whether the reference you have is indeed a hash ref, but put this way the condition is pretty much useless. Since you try a hash dereference first, if the ref isn't a hash ref your code will die before it gets to the test.

    You'd have to swap the parts for them to make sense: 

    if ( ref $ref eq 'HASH' && %$ref ) {

    [download]
    Anno
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