list catenation question

list catenation question

[Steve McConnel]

Using rc 1.1gamma, the following operation acted like I expected:
	(./ /u/bin/)^(fixytab fixycode)
produces
	./fixytab /u/bin/fixycode
I'm not sure that I like pairwise expansion, but since it's documented,
I expected it.  However, the following operation surprised me:
	(. /u/bin)^/fixy^(tab code)
also produces
	./fixytab /u/bin/fixycode
Thinking about this, I guess it must be the correct behavior, but it was
a surprise!  I guess my experience with csh's and bash's {,,} lists has
corrupted my mental model of list expansions to expect cross products
rather than dot products. :-(  Is there any way to get a cross product
other than with a for loop?
--
Stephen McConnel                      UUCP: ...!{convex|utafll}!txsil!steve
Summer Institute of Linguistics   Internet: steve@txsil.sil.org
Dallas, Texas                          (or) steve@utafll.uta.edu

Re: list catenation question, and a plea for reading the archives

[John Mackin]

Steve McConnel asks:

    Is there any way to get a cross product other than with a for loop?

One of the reasons Boyd got annoyed with the rc list is that it is
beginning to rehash issues that have already been discussed.  First we
had people wondering about DEFAULTTOSH, and now we have cross products
_again_!  (Steve, the answer is a definite yes; see below.)  Byron:
can you please have a canned message that you send out to new list
subscribers that _seriously encourages_ them to ftp and read the list
archive before bringing things up on the list?  I am sure you tell them
that it exists, but I don't think that by itself is quite enough -- I
think we need to point out that many of these things have already been
thought through and dealt with, and that if they have further comments
to make they should be made in the light of the previous discussion.

Now, Steve, I quote from the other half of the Sydney rc Mafia, my
friend and Bridge-partner Solid Hogan.  Enjoy!

OK,
John.

From: David Hogan <dhog@cs.su.oz.au>
Date: Thu, 4 Jul 1991 03:48:41 -0500
To: Rc mailing list <rc@archone.tamu.edu>
Subject: Re: username expansion, gnu readline, and code bloat
In-Reply-To: <9107021725.AA00431@roycroft.adobe.com>
Message-Id: <9107041848.17532.out.babuz@cs.su.oz.au>

[...]

[Now we move on to cross products: ]

> needed it:  so far, twice since i switched to rc as my full-time shell.  (six
> months or so.)  wanted it: a dozen or so times more.  often i do an `{ls|egrep}
> or somesuch where ^^ would have been far more convenient.

Well, you could have used the following trick I just worked out:

; z1=(a b c d)
; z2=(x y z)
; eval echo $z1 ^ '^(' ^ $^z2 ^ ')'
ax ay az bx by bz cx cy cz dx dy dz

And what could be simpler but to wrap this up in a shell function where
it'll always be there, just when you need it?  (You can turn the string
returned into a list, but this is trivial).  Of course, this will break
if one of the lists contains strings with spaces in them.  If you are
worried about that you could always use a single for loop, as follows:

foo=()
for (i in $z1) foo = ( $foo $i ^ $z2 )

You see, rc doesn't need built in cross products.

[...]