bar='#pat'; ${foo/$bar/...} problem

bar='#pat'; ${foo/$bar/...} problem

[Andrej Borsenkow]

It seems to be impossible to specify `#' (and probably `%') as part of the
replaced pattern:

bor@itsrm2:/tools/src/zsh-3.1.5-pws-14%> zsh -f
itsrm2% foo=(xxya xxyb)
itsrm2% bar=('xx' 'zz')
itsrm2% print ${foo/$bar[1]/$bar[2]}
zzya zzyb
itsrm2% bar=('#xx' 'zz')
itsrm2% print ${foo/$bar[1]/$bar[2]}
xxya xxyb
itsrm2% print ${foo/$~bar[1]/$bar[2]}
xxya xxyb
itsrm2% setopt extendedglob
itsrm2% print ${foo/$bar[1]/$bar[2]}
xxya xxyb
itsrm2% print ${foo/$~bar[1]/$bar[2]}
zsh: bad pattern: #xx
itsrm2% bar=('\#xx' 'zz')
itsrm2% print ${foo/$~bar[1]/$bar[2]}
xxya xxyb
itsrm2% print ${foo/$bar[1]/$bar[2]}
xxya xxyb
itsrm2%

Only the frirst one yields the correct result. But I need exactly the
run-time pattern, that should match only at the beginning ...

cheers

/andrej

Re: bar='#pat'; ${foo/$bar/...} problem

[Bart Schaefer]

On Apr 1,  6:04pm, Andrej Borsenkow wrote:
} Subject: bar='#pat'; ${foo/$bar/...} problem
}
} It seems to be impossible to specify `#' (and probably `%') as part of the
} replaced pattern:

What you mean here is, specify left-anchored or right-anchored patterns,
right?  In that case, the # or % is not "part of the pattern", it's part
of the ${...} syntax.  The rest is just a glob pattern and doesn't have
any built-in notion of "anchored."  So really there are three:

	${foo/pat/rep}		pat --> rep, anywhere in foo
	${foo/#pat/rep}		pat --> rep, at left of foo
	${foo/%pat/rep}		pat --> rep, at right of foo

Once you get that, it's easy to see that what you're attempting is the
same as if you did

	% bar=('/#xx' '/zz'}
	% print ${foo$bar[1]$bar[2]}

which you obviously wouldn't expect to work (I hope).

Now, you might argue that the implementation of /# and /% should be as
if # and % are extensions of the glob syntax, and in fact that is how
it appears to be implemented in bash:

	$ foo=xxya
	$ bar='#xx'
	$ echo ${foo/$bar/zz}
	zzya

In the meantime, though, you need an eval step of some kind:

	% foo=(xxya xxyb)
	% bar=('#xx' 'zz')
	% eval print '${foo/'"$bar[1]"'/$bar[2]}'

(Did I get to be article 6000? :-)

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

PATCH: 3.1.5-pws-14: Re: bar='#pat'; ${foo/$bar/...} problem

[Bart Schaefer]

On Apr 2,  2:39am, Bart Schaefer wrote:
} Subject: Re: bar='#pat'; ${foo/$bar/...} problem
}
} Now, you might argue that the implementation of /# and /% should be as
} if # and % are extensions of the glob syntax

Index: Src/subst.c
===================================================================
--- subst.c	1999/03/29 21:45:50	1.22
+++ subst.c	1999/04/02 11:06:21
@@ -1361,7 +1361,19 @@
 			 NULL, s[-1]);
 		    return NULL;
 		}
-	    singsub(&s);
+	    {
+		char t = s[-1];
+
+		singsub(&s);
+		if (t == '/' && (flags & SUB_SUBSTR)) {
+		    if (*s == '#' || *s == '%') {
+			flags &= ~SUB_SUBSTR;
+			if (*s == '%')
+			    flags |= SUB_END;
+			s++;
+		    }
+		}
+	    }
 
 	    if (!vunset && isarr) {
 		char **ap = aval;

} (Did I get to be article 6000? :-)

(Hopefully, I did a better job of patching than I did of noticing which
message's headers I was reading the X-Seq: from.  Hard to be 6000 when
that's the one you're replying to.)

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

PATCH: Re: PATCH: 3.1.5-pws-14: Re: bar='#pat'; ${foo/$bar/...} problem

[Bart Schaefer]

On Apr 2,  3:13am, Bart Schaefer wrote:
} Subject: PATCH: 3.1.5-pws-14: Re: bar='#pat'; ${foo/$bar/...} problem
}
} Hopefully, I did a better job of patching than I did of noticing which
} message's headers I was reading the X-Seq: from.

Not too bad, but I noticed that bash lets you quote the leading # or %
like this: ${foo/\\$pat/$repl}

I think this handles it:

Index: Src/subst.c
===================================================================
--- subst.c	1999/04/02 11:26:29	1.23
+++ subst.c	1999/04/02 11:27:33
@@ -1371,6 +1371,8 @@
 			if (*s == '%')
 			    flags |= SUB_END;
 			s++;
+		    } else if (*s == '\\') {
+			s++;
 		    }
 		}
 	    }

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com