Wrap Result in Python API (#4473)

This PR would change the Python API to wrap the C++ Result class instead of translating it to a pure Python class. This is more convenient because there are several possibilities other than sat/unsat/unknown. Furthermore, this PR updates the bitvectors.py example which had an incorrect function name "checkEntailment" and adds a floating point example contributed by Eva Darulova.

2 files changed, 83 insertions, 1 deletions

diff --git a/examples/api/python/bitvectors.py b/examples/api/python/bitvectors.py
index 8e4e1b682..f12e79541 100755
--- a/examples/api/python/bitvectors.py
+++ b/examples/api/python/bitvectors.py
@@ -84,7 +84,7 @@ if __name__ == "__main__":
 
     print("Checking entailment assuming:", new_x_eq_new_x_)
     print("Expect ENTAILED.")
-    print("CVC4:", slv.checkEntailment(new_x_eq_new_x_))
+    print("CVC4:", slv.checkEntailed(new_x_eq_new_x_))
     print("Popping context.")
     slv.pop()
 
diff --git a/examples/api/python/floating_point.py b/examples/api/python/floating_point.py
new file mode 100755
index 000000000..c92666c0b
--- /dev/null
+++ b/examples/api/python/floating_point.py
@@ -0,0 +1,82 @@
+#!/usr/bin/env python
+
+#####################
+#! \file floating_point.py
+ ## \verbatim
+ ## Top contributors (to current version):
+ ##   Eva Darulova, Makai Mann
+ ## This file is part of the CVC4 project.
+ ## Copyright (c) 2009-2018 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.\endverbatim
+ ##
+ ## \brief A simple demonstration of the solving capabilities of the CVC4
+ ## floating point solver through the Python API contributed by Eva
+ ## Darulova. This requires building CVC4 with symfpu.
+
+import pycvc4
+from pycvc4 import kinds
+
+if __name__ == "__main__":
+    slv = pycvc4.Solver()
+    slv.setOption("produce-models", "true")
+    slv.setLogic("FP")
+
+    # single 32-bit precision
+    fp32 = slv.mkFloatingPointSort(8, 24)
+
+    # the standard rounding mode
+    rm = slv.mkRoundingMode(pycvc4.RoundNearestTiesToEven)
+
+    # create a few single-precision variables
+    x = slv.mkConst(fp32, 'x')
+    y = slv.mkConst(fp32, 'y')
+    z = slv.mkConst(fp32, 'z')
+
+    # check floating-point arithmetic is commutative, i.e. x + y == y + x
+    commutative = slv.mkTerm(kinds.FPEq, slv.mkTerm(kinds.FPPlus, rm, x, y), slv.mkTerm(kinds.FPPlus, rm, y, x))
+
+    slv.push()
+    slv.assertFormula(slv.mkTerm(kinds.Not, commutative))
+    print("Checking floating-point commutativity")
+    print("Expect SAT (property does not hold for NaN and Infinities).")
+    print("CVC4:", slv.checkSat())
+    print("Model for x:", slv.getValue(x))
+    print("Model for y:", slv.getValue(y))
+
+    # disallow NaNs and Infinities
+    slv.assertFormula(slv.mkTerm(kinds.Not, slv.mkTerm(kinds.FPIsNan, x)))
+    slv.assertFormula(slv.mkTerm(kinds.Not, slv.mkTerm(kinds.FPIsInf, x)))
+    slv.assertFormula(slv.mkTerm(kinds.Not, slv.mkTerm(kinds.FPIsNan, y)))
+    slv.assertFormula(slv.mkTerm(kinds.Not, slv.mkTerm(kinds.FPIsInf, y)))
+
+    print("Checking floating-point commutativity assuming x and y are not NaN or Infinity")
+    print("Expect UNSAT.")
+    print("CVC4:", slv.checkSat())
+
+    # check floating-point arithmetic is not associative
+    slv.pop()
+
+    # constrain x, y, z between -3.14 and 3.14 (also disallows NaN and infinity)
+    a = slv.mkFloatingPoint(8, 24, slv.mkBitVector("11000000010010001111010111000011", 2))  # -3.14
+    b = slv.mkFloatingPoint(8, 24, slv.mkBitVector("01000000010010001111010111000011", 2))  # 3.14
+
+    bounds_x = slv.mkTerm(kinds.And, slv.mkTerm(kinds.FPLeq, a, x), slv.mkTerm(kinds.FPLeq, x, b))
+    bounds_y = slv.mkTerm(kinds.And, slv.mkTerm(kinds.FPLeq, a, y), slv.mkTerm(kinds.FPLeq, y, b))
+    bounds_z = slv.mkTerm(kinds.And, slv.mkTerm(kinds.FPLeq, a, z), slv.mkTerm(kinds.FPLeq, z, b))
+    slv.assertFormula(slv.mkTerm(kinds.And, slv.mkTerm(kinds.And, bounds_x, bounds_y), bounds_z))
+
+    # (x + y) + z == x + (y + z)
+    lhs = slv.mkTerm(kinds.FPPlus, rm, slv.mkTerm(kinds.FPPlus, rm, x, y), z)
+    rhs = slv.mkTerm(kinds.FPPlus, rm, x, slv.mkTerm(kinds.FPPlus, rm, y, z))
+    associative = slv.mkTerm(kinds.Not, slv.mkTerm(kinds.FPEq, lhs, rhs))
+
+    slv.assertFormula(associative)
+
+    print("Checking floating-point associativity")
+    print("Expect SAT.")
+    print("CVC4:", slv.checkSat())
+    print("Model for x:", slv.getValue(x))
+    print("Model for y:", slv.getValue(y))
+    print("Model for z:", slv.getValue(z))