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#!/usr/bin/env python
#####################
## sygus-inv.py
## Top contributors (to current version):
## Yoni Zohar
## This file is part of the CVC4 project.
## Copyright (c) 2009-2020 by the authors listed in the file AUTHORS
## in the top-level source directory and their institutional affiliations.
## All rights reserved. See the file COPYING in the top-level source
## directory for licensing information.
##
## A simple demonstration of the solving capabilities of the CVC4
## sygus solver through the Python API. This is a direct
## translation of sygus-inv.cpp .
##
import pycvc4
from pycvc4 import kinds
if __name__ == "__main__":
slv = pycvc4.Solver()
# required options
slv.setOption("lang", "sygus2")
slv.setOption("incremental", "false")
# set the logic
slv.setLogic("LIA")
integer = slv.getIntegerSort()
boolean = slv.getBooleanSort()
zero = slv.mkReal(0)
one = slv.mkReal(1)
ten = slv.mkReal(10)
# declare input variables for functions
x = slv.mkVar(integer, "x")
xp = slv.mkVar(integer, "xp")
# (ite (< x 10) (= xp (+ x 1)) (= xp x))
ite = slv.mkTerm(kinds.Ite,
slv.mkTerm(kinds.Lt, x, ten),
slv.mkTerm(kinds.Equal, xp, slv.mkTerm(kinds.Plus, x, one)),
slv.mkTerm(kinds.Equal, xp, x))
# define the pre-conditions, transition relations, and post-conditions
pre_f = slv.defineFun("pre-f", {x}, boolean, slv.mkTerm(kinds.Equal, x, zero))
trans_f = slv.defineFun("trans-f", {x, xp}, boolean, ite)
post_f = slv.defineFun("post-f", {x}, boolean, slv.mkTerm(kinds.Leq, x, ten))
# declare the invariant-to-synthesize
inv_f = slv.synthInv("inv-f", {x})
slv.addSygusInvConstraint(inv_f, pre_f, trans_f, post_f)
# print solutions if available
if slv.checkSynth().isUnsat():
# Output should be equivalent to:
# (define-fun inv-f ((x Int)) Bool (not (>= x 11)))
slv.printSynthSolution()
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