examples/SimpleVC.py

   1 #! /usr/bin/python
   2 ##! \file SimpleVC.py
   3 ### \verbatim
   4 ### Original author: mdeters
   5 ### Major contributors: none
   6 ### Minor contributors (to current version): none
   7 ### This file is part of the CVC4 prototype.
   8 ### Copyright (c) 2009, 2010, 2011  The Analysis of Computer Systems Group (ACSys)
   9 ### Courant Institute of Mathematical Sciences
  10 ### New York University
  11 ### See the file COPYING in the top-level source directory for licensing
  12 ### information.\endverbatim
  13 ###
  14 ### \brief A simple demonstration of the Python interface
  15 ###
  16 ### A simple demonstration of the Python interface.  Compare to the
  17 ### C++ interface in simple_vc_cxx.cpp; they are quite similar.
  18 ###
  19 ### To run, use something like:
  20 ###
  21 ###   ln -s ../builds/src/bindings/python/CVC4.py CVC4.py
  22 ###   ln -s ../builds/src/bindings/python/.libs/CVC4.so _CVC4.so
  23 ###   ./SimpleVC.py
  24 ####
  25
  26 import CVC4
  27 from CVC4 import ExprManager, SmtEngine, Rational, Expr
  28
  29 import sys
  30
  31 def main():
  32   em = ExprManager()
  33   smt = SmtEngine(em)
  34
  35   # Prove that for integers x and y:
  36   #   x > 0 AND y > 0  =>  2x + y >= 3
  37
  38   integer = em.integerType()
  39
  40   x = em.mkVar("x", integer)
  41   y = em.mkVar("y", integer)
  42   zero = em.mkConst(Rational(0))
  43
  44   x_positive = em.mkExpr(CVC4.GT, x, zero)
  45   y_positive = em.mkExpr(CVC4.GT, y, zero)
  46
  47   two = em.mkConst(Rational(2))
  48   twox = em.mkExpr(CVC4.MULT, two, x)
  49   twox_plus_y = em.mkExpr(CVC4.PLUS, twox, y)
  50
  51   three = em.mkConst(Rational(3))
  52   twox_plus_y_geq_3 = em.mkExpr(CVC4.GEQ, twox_plus_y, three)
  53
  54   formula = Expr(em.mkExpr(CVC4.AND, x_positive, y_positive)).impExpr(Expr(twox_plus_y_geq_3))
  55
  56   print("Checking entailment of formula " + formula.toString() + " with CVC4.")
  57   print("CVC4 should report ENTAILED .")
  58   print("Result from CVC4 is: " + smt.checkEntailed(formula).toString())
  59
  60   return 0
  61
  62 if __name__ == '__main__':
  63   sys.exit(main())
  64