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From: brossard@sic.epfl.ch (Alain Brossard EPFL-SIC/SII)
Newsgroups: comp.lang.perl
Subject: Re: Returning two lists
Message-ID: <1991Apr5.182305@sic.epfl.ch>
Date: 5 Apr 91 16:23:05 GMT
References: <6010@male.EBay.Sun.COM>
Sender: news@sicsun.epfl.ch
Reply-To: brossard@sasun1.epfl.ch
Organization: Ecole Polytechnique Federale de Lausanne
Lines: 50

In article <6010@male.EBay.Sun.COM>, me@anywhere.EBay.Sun.COM (Wayne Thompson - IR Workstation Support SE) writes:
|> --- Alain Brossard writes ---
|>    I want to return two lists from a subroutine
|> 
|> sub search {
|>     local( @list, @whiteouts ) = @_;
|> (...)
|>     return ( @list, @whiteouts );
|> # also tried
|> #   return ( (@list), (@whiteouts) );
|> }
|> 
|> (@list, @whiteouts) = do search( $dir, '' );
|> 
|> 	The only thing I get is that on return, @list
|> always contains the union of the returned lists.
|> -----------------------------
> 
> You could return enough information to decompose the lists...
> 
> return (scalar(@list), @list, @whiteouts);

  Will scalar(ARRAY) always return the size of the array?
I didn't see that documented anywhere.

> Then recompose them on receipt...
> 
> @_ &search(....);
> @whiteouts = splice (@_, shift (@_));
> @list = @_;
> 
> Wayne

  Thanks for pointing me out the splice fonction. I think
the following code is a bit more efficient?

@whiteouts = do search( $dir, '' );
@list = splice( @whiteouts, 0, shift(@whiteouts));

    @list can be potentialy huge, so I was really looking
for the optimal way of doing this.  The best way would be to
(shudder) use global variables, but this is out since the
subroutine is recursive (and not tail-end recursive).


-- 

Alain Brossard, Ecole Polytechnique Federale de Lausanne,
	SIC/SII, EL-Ecublens, CH-1015 Lausanne, Suisse
brossard@sasun1.epfl.ch