Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!timbuk!shamash!rrr
From: rrr@u02.svl.cdc.com (Rich Ragan)
Newsgroups: comp.lang.perl
Subject: Array modification rules (?)
Keywords: splice perl array modifications
Message-ID: <29924@shamash.cdc.com>
Date: 17 Jan 91 18:06:44 GMT
Sender: usenet@shamash.cdc.com
Reply-To: rrr@svl.cdc.com
Organization: Control Data Corporation, Silicon Valley Operations
Lines: 27

I often want to modify the array that is being used as the
iterator for a loop within that loop. Some examples, include
 
- Scan the argument vector and remove or add args based on
  what was specified.
- Scan an array and remove "uninteresting" elements

To be safe, I have always used a temporary array in the
past. Is this necessary or are there well defined rules
for adding/deleting elements from the array being used as
the iterator within the scope of the iteration? 

Will this become patently obvious when my copy of "The Book"
arrives? In any event, I could not contain my curiosity any
longer.

Assuming the rules are formalized and "intuitive" it could
be useful for a lot of cases. I played with the following
little piece to determine that there is some method to what
happens.

@a=split(//,"%xJaubsctd eafngohtihjekrl mPneorplq rhsatcukvewrx");
for (@a) {splice(@a,0,1);$x .= $_;}  print "$x\n";
--
Richard R. Ragan   rrr@svl.cdc.com    (408) 496-4340 
Control Data Corporation - Silicon Valley Operations
5101 Patrick Henry Drive, Santa Clara, CA 95054-1111