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From: phil@ux1.cso.uiuc.edu (Phil Howard KA9WGN)
Newsgroups: comp.lang.perl
Subject: Re: While learning PERL... a suggestion
Keywords: perl file learn suggest
Message-ID: <1991Jan21.201845.28080@ux1.cso.uiuc.edu>
Date: 21 Jan 91 20:18:45 GMT
References: <1991Jan19.003519.23569@ux1.cso.uiuc.edu> <11115@jpl-devvax.JPL.NASA.GOV> <118879@uunet.UU.NET> <1991Jan21.092204.11944@ux1.cso.uiuc.edu> <1991Jan21.174520.12207@iwarp.intel.com>
Organization: University of Illinois at Urbana
Lines: 46

merlyn@iwarp.intel.com (Randal L. Schwartz) writes:

>Arrays of filehandles are not directly supported.  You can use arrays
>of values that are to be assigned into indirect filehandles, like so:

>	$indir = $filehandle[17];
>	print $indir "This goes to the 17th filehandle";

>but you cannot directly do the dereferencing of the array and the I/O
>in the same expression.

My only comment is that this must be a very complex syntax to parse.
The mere existance of space between the handle and the string above
would separate things.  I wonder if there are any cases where the
data to be printed could be an expression with a unary prefix operator
that could cause an apparent ambiguity as to look like a binary infix
operator between the filehandle and the data, thus appearing to be an
expression to be printed on STDOUT.

>You could also futz with the namespace, like:

>	*HANDLE = $filehandle[17];
>	print HANDLE "this goes to the 17th filehandle";

>but remember that this affects &HANDLE, %HANDLE, and @HANDLE as well.
>(I understand that this is more efficient than the indirect filehandle
>if you do more than one I/O per filehandle switch.)

In what way does it affect them?  I was getting the impression from the
man pages that these name spaces were separate.  This was discussed in
the man pages with regard to passing by references, but I guess you are
now filling in the ambiguities of its affect elswhere.  I'm not up on
subroutines yet (probably mostly due to not understand how the name
space works).

>By the way, in this syntax, the filehandle never hits the Perl
>tokenizer, so you are not limited to a standard "name" for your
>filehandle.  You can use "\007smurf city u.s.a. 00001" as your
>filehandle name, for example.  My favorite is something like "0000001"
>in a variable that is being automagically incremented, so I can
>generate them on demand and know that they won't collide with other
>symbol names in my namespace.
-- 

--Phil Howard, KA9WGN-- | Individual CHOICE is fundamental to a free society
<phil@ux1.cso.uiuc.edu> | no matter what the particular issue is all about.