Re: pattern-matching in LISP?

Hi,

But it didn't appear to work. Does LISP have pattern-matching capabilities
as well?

I certainly don't want to keep you from having some fun implementing
your own pattern matcher in Common Lisp, but there are some libraries
readily available that you might be interested in.

First, there is CL-Unification: http://common-lisp.net/project/cl-unification/

CL-USER> (unify:match-case ('(1 2 3 4))
((?x ?y . ?z) (values 'yes (+ x y) z))
(?x (values 'no x)))
YES
3
(3 4)
CL-USER> (unify:match-case ('(1))
((?x ?y . ?z) (values 'yes (+ x y) z))
(?x (values 'no x)))
NO
(1)

Second, Faré Ridaeu's matching library, fare-matcher: http://www.cliki.net/fare-matcher

CL-USER> (fare-matcher:match '(1 2 3 4)
((list* x y z) (values 'yes (+ x y) z))
(x (values 'no x)))
YES
3
(3 4)
CL-USER> (fare-matcher:match '(1)
((list* x y z) (values 'yes (+ x y) z))
(x (values 'no x)))
NO
(1)

Third, the pattern matcher included in the ARNESI library:
http://common-lisp.net/project/bese/arnesi.html

CL-USER> (arnesi:match-case '(1 2 3 4)
((:list* x y z) (values 'yes (+ x y) z))
(x (values 'no x)))
YES
3
(3 4)
CL-USER> (arnesi:match-case '(1)
((:list* x y z) (values 'yes (+ x y) z))
(x (values 'no x)))
NO
(1)

Finally, I just stumbled upon MCPat, but I don't really know what
exactly it's supposed to be and how to use it: http://www.sfmishras.com/smishra/mcpat/

As I haven't actually used any of these libraries, I can't make a
recommendation. Just choose the one which looks the nicest to you or
whatever. :)

Bye-bye,
Matthias

.

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