Re: Pass on name of array

You can make a sub accept an array and you can act on it without knowing the 'name' of the array you are receiving. This is done with references:

sub DoSomethingToArray (\@)
{
      my ($array) = @_;

      for ($br = 0; $br <= $#{$array}; $br++)
      {
            # Do stuff with @$array using references
      }
}

# Call it simply as:
DoSomethingToArray(@config::a);
DoSomethingToArray(@config::b);
DoSomethingToArray(@config::c);
[download]

Note that this function has a prototype which tells Perl that you don't want the array (@), but a reference to it. Without this prototype, the contents of the array are passed to the function, which is of less use.

Update: Changed '<' comparison to '<=' in the for loop as per ton's correction below.

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Re: Re: Pass on name of array by ton (Friar) on Apr 05, 2001 at 21:49 UTC
Quick note: if you use the above solution, change the '<' in the conditional of the for loop to '<='. e.g.: `for ($br = 0; $br <= $#{$array}; $br++)` [download] '#' when applied to arrays returns the last valid index, so a less than conditional will fail on the last valid index, meaning that index will never be used. Alternately, you could use the size of the array: `for ($br = 0; $br <= @$array; $br++)` [download] or, to eliminate any ambiguity, `for ($br = 0; $br <= scalar(@$array); $br++)` [download]	[reply] [d/l] [select]
Re: Re: Re: Pass on name of array by merlyn (Sage) on Apr 05, 2001 at 21:52 UTC
`for ($br = 0; $br <= scalar(@$array); $br++)` [download] Please don't add the extra `scalar`. It confuses your maintainer, unless you comment it as `# we don't need scalar here... it's for the dummies who can't grok sca +lar context yet` [download] So I would fail it out of a code review without that comment. If someone doesn't understand that `<=` provides scalar context, they have no business editing my code. -- Randal L. Schwartz, Perl hacker	[reply] [d/l] [select]
Re (tilly) 4: Pass on name of array by tilly (Archbishop) on Apr 06, 2001 at 12:29 UTC
I think that is too harsh. I often put scalar in when it is not neededfor the same reason that I use parens which are not needed - I know that the code is likely to be edited by someone who has not memorized the various contexts. Now in a perfect all Perl world, I would agree with you. But when my code needs to be understood by programmers who are not primarily Perl programmers, well I am confident that I can teach them to remember that Perl has both scalar and list contexts, and they do different things. But when they have to edit my Perl after a month in other languages, I do not believe that they will retain fast reactions for which syntactic constructs imply scalar context. So I leave in the crutch, and since everyone knows that I do this deliberately, I don't see any reason to comment it. OTOH in code which will only be seen by people who are supposed to be competent Perl programmers, well I drop it...	[reply]