Z3 pattern matching syntax

Question

I'm trying to use pattern matching in z3 to work with algebraic datatypes. I'm exactly following the syntax given in the SMTLib standard on page 27, but z3 is giving me a syntax error. For example in the following program:

(declare-datatype Dyn ((a) (b)))
(define-fun foo ((x Dyn)) Int (
  match x (
    (a 1)
    (b 2)
  )
))
(assert (= (foo a) (1)))
(check-sat)

it gives me the error "line 4 column 7: variable symbol expected". As far as I can tell I'm following the specified syntax exactly. How do I fix this?

As of Feb 3rd 2018, building z3 from github sources, this program is accepted just fine. Looks like they fixed the bug! — alias, Feb 04 '19 at 01:49
Great! I opened an issue about this on their github and they closed it, so it's good that it is indeed fixed! — vijrox, Feb 04 '19 at 06:06

score 1 · Accepted Answer · answered Jan 28 '19 at 07:03

I don't think you're doing anything wrong! Looks like this is a z3 bug that you should report at https://github.com/Z3Prover/z3/issues/

There's one little problem with your assert statement right before (check-sat). It should read:

(assert (= (foo a) 1))

i.e., without any parenthesis around 1. But your use of the match command is syntactically correct and should be reported as a z3 bug.

Z3 pattern matching syntax

1 Answers1