Re^2: Truthfulness of references

[njcodewarrior]

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
}

or...

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

Thanks again for your help.
njcodewarrior

[Anno]

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
}

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
}

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 ) {

Anno