[Chicago-talk] \1 vs $1

Andy_Bach at wiwb.uscourts.gov Andy_Bach at wiwb.uscourts.gov
Wed Nov 3 12:42:34 CST 2004

I just read a post:
> ... and \1 is deprecated for $1.

and having stumbled over this recently, I was a little suprised to hear of 
the deprecation.  What I'd found was \1 isn't the same as $1, in that

deletes duplicate chars, while;

depends upon the value of $1 - which, in this case'd be set *before* the 
subst got invoked!  On the right hand side, $1 is what we expect but \1 
also can change during the course of a regex evaluation - as the 
parser/matcher works, \1 will take on different values during backtracking 
etc - though, in the end \1 is the same as $1.

Er, am I all wet here?


Andy Bach, Sys. Mangler
Internet: andy_bach at wiwb.uscourts.gov 
VOICE: (608) 261-5738  FAX 264-5932

"If there be time to expose through discussion the falsehood and 
fallacies, to avert the evil
by the process of education, the remedy to be applied is more speech, not 
enforced silence." 
   Justice Louis Brandeis

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