three smt2 examples added and one python example updated (#5690)

examples/python/bounded model checking/bubble_sort.py

@@ -1,4 +1,6 @@
-# BUBBLESORT  -  Copyright (c) June, 2020 - Matteo Nicoli
+#    File name:    bubble_sort.py
+#
+#    BUBBLESORT  -  Copyright (c) June, 2020 - Matteo Nicoli
 
 from z3 import Solver, Int, Array, IntSort, And, Not, If, Select, Store, sat
 
@@ -36,34 +38,56 @@ def check(variables, Ar, dim) :
         yield variables[e] == Select(Ar,e)
 
 def mk_post_condition(values) :
-    condition = []
-    for v1,v2 in zip(values,values[1:]) :
-        condition.append(v1 <= v2)
+    condition = [v1 <= v2 for v1,v2 in zip(values,values[1:])]
     return And(*condition)
 
-dim = int(input("size of the array: "))
 
-i = [Int(f"i_{x}") for x in range(dim + 1)]
-j = [Int(f"j_{x}") for x in range(dim + 1)]
-A = [Array(f"A_{x}",IntSort(),IntSort()) for x in range(dim + 1)]
-tmp = [Int(f"tmp_{x}") for x in range(dim)]
+def main() :
+    dim = int(input("size of the array: "))
 
-s = Solver()
+    i = [Int(f"i_{x}") for x in range(dim + 1)]
+    j = [Int(f"j_{x}") for x in range(dim + 1)]
+    A = [Array(f"A_{x}",IntSort(),IntSort()) for x in range(dim + 1)]
+    tmp = [Int(f"tmp_{x}") for x in range(dim)]
 
-init_condition = init(i[0],j[0])
-s.add(init_condition)
+    s = Solver()
 
-tran_condition= mk_tran_condition(A, i, j, tmp, dim)
-s.add(And(*tran_condition))
+    init_condition = init(i[0],j[0])
+    s.add(init_condition)
 
-values = [Int(f"n_{x}") for x in range(dim)]
-init_check_condition = check(values,A[-1],dim)
-s.add(And(*init_check_condition))
+    tran_condition = mk_tran_condition(A, i, j, tmp, dim)
+    s.add(And(*tran_condition))
 
-post_condition = mk_post_condition(values)
-s.add(Not(post_condition))
+    values = [Int(f"n_{x}") for x in range(dim)]
+    init_check_condition = check(values,A[-1],dim)
+    s.add(And(*init_check_condition))
 
-if s.check() == sat :
-    print(f"counterexample:\n{s.model()}")
-else :
-    print("valid")
+    post_condition = mk_post_condition(values)
+
+    print("Bubble sort")
+    print("---------------------")
+
+    s.push()
+    s.add(Not(post_condition))
+
+    print("Testing the validity of the algorithm; `valid expected`:")
+
+    if s.check() == sat :
+        print(f"counterexample:\n{s.model()}")
+    else :
+        print("valid")
+
+    print("---------------------")
+
+    s.pop()
+
+    s.add(post_condition)
+    print("Getting a model...")
+    print("Model:")
+
+    if s.check() == sat :
+        print(s.model())
+
+
+if __name__ == "__main__" :
+    main()