z3py throws parser error for a valid SMT2 file

Question

 1  (set-logic UFLIA)
 2  (set-info :source | Simple list theorem |)
 3  (set-info :smt-lib-version 2.0)
 4  (set-info :category "crafted")
 5  (set-info :status unsat)
 6  (declare-sort List 0)
 7  (declare-sort Elem 0)
 8  (declare-fun cons (Elem List) List)
 9  (declare-fun nil () List)
10  (declare-fun car (List) Elem)
11  (declare-fun cdr (List) List)
12  (declare-fun len (List) Int)
13  (assert (forall ((?x Elem) (?y List)) (= (car (cons ?x ?y)) ?x)))
14  (assert (forall ((?x Elem) (?y List)) (= (cdr (cons ?x ?y)) ?y)))
15  (assert (= (len nil) 0))
16  (assert (forall ((?x Elem) (?y List)) (= (len (cons ?x ?y)) (+ (len ?y) 1))))
17  (declare-fun append (List List) List)
18  (assert (forall ((?y List)) (= (append nil ?y) ?y)))
19  (assert (forall ((?x Elem) (?y1 List) (?y2 List)) (= (append (cons ?x ?y1) ?y2) (cons ?x (append ?y1 ?y2)))))
20  (assert (not (forall ((?x Elem) (?y List)) (= (append (cons ?x nil) ?y) (cons ?x ?y)))))
21  (check-sat)
22  (exit)

For the above formula, f = z3.parse_smt2_file("UFLIA/misc/list3.smt2") results in the following errors.

(error "line 6 column 14: invalid sort declaration, sort already declared/defined")
(error "line 8 column 24: sort constructor expects parameters")
(error "line 9 column 20: sort constructor expects parameters")
(error "line 10 column 18: sort constructor expects parameters")
(error "line 11 column 18: sort constructor expects parameters")
(error "line 12 column 18: sort constructor expects parameters")
(error "line 13 column 31: sort constructor expects parameters")
(error "line 14 column 31: sort constructor expects parameters")
(error "line 15 column 16: unknown constant nil")
(error "line 16 column 31: sort constructor expects parameters")
(error "line 17 column 21: sort constructor expects parameters")
(error "line 18 column 21: sort constructor expects parameters")
(error "line 19 column 32: sort constructor expects parameters")
(error "line 20 column 36: sort constructor expects parameters")

But processing the same file with z3-4.3.2.bb56885147e4-x64-osx-10.9.2 CLI provides unsat result.

Using traceback in Python, I found the following as the root cause of the exception TypeError: unorderable types: int() < Z3Exception() Based on the exception stack, it seems the error is stemming from within native Z3 code.

Any idea why is this happening and how to resolve this?

Answer 1

You will have to rename "List" to something else. From the API, Z3 pre-loads a built-in definition for "List". It ignores the logic directive that otherwise narrows the pre-loaded sort.

Answer 2

Based on @nikolaj comment, I used the following function to transform SMT2 files by renaming identifiers that clashed with definitions pre-loaded by Z3 when using Z3 API. [In addition to List , the function renames identifiers that are commonly used in SMT-LIB formulae.]

import z3
import importlib

def get_formula(src_file_name):
  try:
    f = z3.parse_smt2_file(src_file_name)
    return f
  except z3.Z3Exception as e:
    lines = open(src_file_name, 'rt').readlines()
    tmp1 = ' '.join(lines).replace("max", "c_max")
    tmp1 = tmp1.replace("sin", "c_sin")
    tmp1 = tmp1.replace("cos", "c_cos")
    tmp1 = tmp1.replace("tan", "c_tan")
    tmp1 = tmp1.replace("tanh", "c_tanh")
    tmp1 = tmp1.replace("atan", "c_atan")
    tmp1 = tmp1.replace("min", "c_min")
    tmp1 = tmp1.replace("max", "c_max")
    tmp1 = tmp1.replace("pi", "c_pi")
    tmp1 = tmp1.replace("List", "c_List")
    tmp1 = tmp1.replace("subset", "c_subset")
    tmp1 = tmp1.replace("difference", "c_difference")
    tmp1 = tmp1.replace("union", "c_union")
    tmp1 = tmp1.replace("fp", "c_fp")
    tmp1 = tmp1.replace("repeat", "c_repeat")
    importlib.reload(z3)
    f = z3.parse_smt2_string(tmp1)
    return f

With this function, I was able to successfully parse the formula but the program seg-faulted upon exit . It seems that there are some references that aren't cleaned up even after reloading z3 module.