Re: backreferences

[Ray Andrews <rayandrews@eastlink.ca>]

On 10/16/2015 08:33 PM, Bart Schaefer wrote:

> Only seems to. Try sstring="edcbaabcdeedcbaabcde" and I don't think 
> you'll get the result you expected. 

Correct.  It fails if the very start of the string is the negation, 
which seems strange.  Any change at all to the 'bait' leading 'edcba' 
fixes it.  The empty string is the intuitive expectation for match[1].
>>> This needs to be (#b)(^edcba*)(edcba)(*)
... and that does indeed seem to cover every situation that I've tried.  
Am I correct in reading the '*' as saying: "Anything OR NOTHING in front 
of 'edcba' "?  That's not hard to fathom.  Anyway I guess the difference 
is something that could be put to use in some conceivable situation. BTW 
does sed have that functionality?  I did quite a bit of research and 
came up with nothing.  Even at StackExchange no one had an answer, but 
it seems to me like a very fundamental sort of thing.  Cool if zsh can 
do something that sed can't tho you'd hardly expect that to be the case.
>> There might be something in the Bash to Zsh book -- I don't have it 
>> handy to confirm. 
Nope, nothing that I can find.