[cl-ppcre-devel] register-groups-bind tests all groups for nil

[Kick Damien-DKICK1]

Consider the following

; CLISP  Port: 1604  Pid: 3572
CL-USER> 
PG-USER> (register-groups-bind (x y z)
             ('(:sequence
                (:alternation (:register #\a) #\1)
                (:alternation (:register #\b) #\2)
                (:alternation (:register #\c) #\3))
               "123")
           (values x y z))
NIL
NIL
NIL
PG-USER> (register-groups-bind (x y z)
             ('(:sequence
                (:alternation (:register #\a) #\1)
                (:alternation (:register #\b) #\2)
                (:alternation (:register #\c) #\3))
               "abc")
           (values x y z))
"a"
"b"
"c"
PG-USER>  

-----Original Message-----
From: cl-ppcre-devel-bounces at common-lisp.net
[mailto:cl-ppcre-devel-bounces at common-lisp.net] On Behalf Of
dsb at prairienet.org
Sent: Friday, April 06, 2007 10:09 AM
To: cl-ppcre-devel at common-lisp.net
Subject: [cl-ppcre-devel] register-groups-bind tests all groups for nil

Using register-groups-bind, sbcl generates a compiler warning if the
user doesn't make sure each bound variable is non-nil before using it.
Since the body is evaluated only if there's a match, testing bound
variables seems kind of redundant for the first N variables, where N is
the number of groups in the regex.

It looks like an IF form in register-groups-bind is the source of the
warning.  It checks all groups for nil-ness, even the first ones.
I thought variables that match groups would be guaranteed to be non-nil.
I would be nice to be able to use matching variables immediately as long
as the user is careful not to bind extra ones.

I guess eliminating individual tests for bound groups would require that
scan returns another value containing the number of matches, or
truncates the register-groups array so that the number of matches
is just the length of the array.   Then matching variables could be
bound directly, and extras could be set to nil without the IF.

--Dan
prairienet.org/~dsb/

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