Three ways to assgin values to an array in z3

Question

As far as I know, there are three ways to assgin values to an array in z3.

1. use assert to assgin values to some of the cells:

(declare-const a1 (Array Int Int))
(declare-const a2 (Array Int Int))

(assert (= 1 (select a1 0)))
(assert (= 2 (select a2 0)))

z3 returns unsat when the constraint (assert (= a1 a2)) is added.

2. use as const to initialize the array first and then assgin values to specific cells:

(declare-const a3 (Array Int Int))
(assert
    (=
        (store ((as const (Array Int Int)) 64) 0 3)
        a3
    )
)
(declare-const a4 (Array Int Int))
(assert
    (=
        (store ((as const (Array Int Int)) 64) 0 4)
        a4
    )
)

Add (assert (= a3 a4)) and we obtain unsat again.

3. define the array via a function:

(define-const a5 (Array Int Int)
    (lambda ((i Int))
    (ite (= i 0) 5 64)))
(define-const a6 (Array Int Int)
    (lambda ((i Int))
    (ite (= i 0) 6 64)))

But if we add (assert (= a5 a6)), z3 returns sat. Why?

By the way, is there any (better) way to assign values to an array in z3?

Answer 1

It's a bug. Check out this issue.