Re^2: Hash of arrays of arrays

Many thanks to all who contributed in answer to my query - with the help of the Perl Monks, I am now most of the way there (though I had to dump the database idea in favour of a flat file - such is life!).

However, I do have one small puzzle remaining, which perhaps someone could help me with:

In one place, I need to add another record to my array of records, but only after checking all other records associated with that key, to make sure that the record I am adding is not a duplicate.

So I need to test if I am at the end of the array, by checking a counter variable against the number of elements in the records array for the current key. I would have thought that the correct code would be along the lines of:

if ($i < @{$db{$key}})
   ...
[download]

This is similar to the 'for' loop in ikegami's excellent example code. And I have seen something similar used in other code samples concerning hash-of-arrays structures. But when I print out the value of '@{$db{$key}}', I get:

ARRAY(0xfdb30)
[download]

Obviously, I would have expected to get an integer. Does the fact that my array elements contain another level of arrays (unlike the other examples I have seen) mean that I need a different test? Or is this simply a side-effect of 'print'?

Can I rely on using '@{$db{$key}}' in my test, or would anyone like to suggest something different??

Thanks in advance for any further guidance you can give me!

Graham Scott.

Comment on Re^2: Hash of arrays of arrays Select or Download Code

Replies are listed 'Best First'.
Re^3: Hash of arrays of arrays by ikegami (Patriarch) on Oct 08, 2004 at 19:05 UTC
Compare: `$\=$/; @a = qw( d e f ); print(@a); # prints 'def' print(scalar(@a)); # prints '3' print(@a==3?'3':'!3'); # prints '3'` [download] `print` accepts a list as an argument. `@array` returns a list of its elements in a list context. `<` accepts scalars as arguments. `@array` returns the number of elements it has in a scalar context. So yes, you can rely on `@{$db{$key}}` for your test. If you want to make it clear to yourself, use `scalar(@{$db{$key}})` instead.	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^3: Hash of arrays of arrays
by ikegami (Patriarch) on Oct 08, 2004 at 19:05 UTC

Compare:

$\=$/;
@a = qw( d e f );
print(@a);               # prints 'def'
print(scalar(@a));       # prints '3'
print(@a==3?'3':'!3');   # prints '3'
[download]

print accepts a list as an argument. @array returns a list of its elements in a list context.

< accepts scalars as arguments. @array returns the number of elements it has in a scalar context.

So yes, you can rely on @{$db{$key}} for your test. If you want to make it clear to yourself, use scalar(@{$db{$key}}) instead.

[reply]
[d/l]
[select]