Re: order of processing in brace expansion

[Peter Stephenson <pws@csr.com>]

Allan Poindexter <apoindex@aoc.nrao.edu> wrote:
> Consider the following:
> 
> pts/11 10:37 208%setopt braceccl
> pts/11 10:38 209%foo=b,c
> pts/11 10:38 210%echo a{$foo}d
> a,d abd acd
> 
> Can anyone shed any light on what I might be overlooking here?

By default, parameters in zsh are expanded without turning the contents
into tokens, so the comma is just treated as a normal character, just as if
you had typed a{'b,c'}d.  This is the behaviour I would expect.

The real bug, I would say, is this:

% echo a{$~foo}d
a,d abd acd

The ~ force $foo to be interpreted pretty much as if the characters had
been put directly on the command line (the option GLOB_SUBST does the same
thing).  This is done by default by a lot of other shells.  In *this* case,
I would expect what you expect: the expression is interpreted the same as
a{b,c}d.  Unfortunately it isn't.  The reason seems to be that the comma
doesn't get turned back into a token.  If we want to fix this, the
following patch will do it.

Index: Src/glob.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/glob.c,v
retrieving revision 1.15
diff -u -r1.15 glob.c
--- Src/glob.c	2001/04/24 05:45:17	1.15
+++ Src/glob.c	2001/04/27 17:57:25
@@ -2373,6 +2373,7 @@
 	case '*':
 	case '?':
 	case '=':
+	case ',':
 	    for (t = ztokens; *t; t++)
 		if (*t == *s) {
 		    if (bslash)

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Unit 300, Science Park, Milton Road,
Cambridge, CB4 0XL, UK                          Tel: +44 (0)1223 392070


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