Support globals to define their own negation

cpmpy/expressions/globalconstraints.py

@@ -134,7 +134,7 @@ def my_circuit_decomp(self):
 
 from .core import BoolVal
 from .utils import all_pairs, is_int, is_bool, STAR
-from .variables import _IntVarImpl
+from .variables import _IntVarImpl, _BoolVarImpl
 from .globalfunctions import * # XXX make this file backwards compatible
 
 
@@ -173,6 +173,14 @@ def get_bounds(self):
         """
         return 0, 1
 
+    def negate(self):
+        """
+        Returns the negation of this global constraint.
+        Defaults to ~self, but subclasses can implement a better version,
+        > Fages, François, and Sylvain Soliman. Reifying global constraints. Diss. INRIA, 2012.
+        """
+        return ~self
+
 
 # Global Constraints (with Boolean return type)
 def alldifferent(args):
@@ -430,6 +438,9 @@ def value(self):
         arrval = argvals(arr)
         return arrval in tab
 
+    def negate(self):
+        return NegativeTable(self.args[0], self.args[1])
+
 class ShortTable(GlobalConstraint):
     """
         Extension of the `Table` constraint where the `table` matrix may contain wildcards (STAR), meaning there are
@@ -479,6 +490,9 @@ def value(self):
         arrval = argvals(arr)
         tabval = argvals(tab)
         return arrval not in tabval
+
+    def negate(self):
+        return Table(self.args[0], self.args[1])
 
 
 class Regular(GlobalConstraint):
@@ -596,6 +610,9 @@ def __repr__(self):
         condition, if_true, if_false = self.args
         return "If {} Then {} Else {}".format(condition, if_true, if_false)
 
+    def negate(self):
+        return IfThenElse(self.args[0], self.args[2], self.args[1])
+
 
 
 class InDomain(GlobalConstraint):
@@ -636,6 +653,11 @@ def value(self):
     def __repr__(self):
         return "{} in {}".format(self.args[0], self.args[1])
 
+    def negate(self):
+        lb, ub = get_bounds(self.args[0])
+        return InDomain(self.args[0],
+                        [v for v in range(lb,ub+1) if v not in set(self.args[1])])
+
 
 class Xor(GlobalConstraint):
     """
@@ -668,6 +690,21 @@ def __repr__(self):
             return "{} xor {}".format(*self.args)
         return "xor({})".format(self.args)
 
+    def negate(self):
+        # negate one of the arguments, ideally a variable
+        new_args = None
+        for i, a in enumerate(self.args):
+            if isinstance(a, _BoolVarImpl):
+                new_args = self.args[:i] + [~a] + self.args[i+1:]
+                break
+
+        if new_args is None:# did not find a Boolean variable to negate
+            # pick first arg, and push down negation
+            new_args = list(self.args)
+            new_args[0] = cp.transformations.negation.recurse_negation(self.args[0])
+
+        return Xor(new_args)
+
 
 class Cumulative(GlobalConstraint):
     """

cpmpy/transformations/negation.py

@@ -117,9 +117,9 @@ def recurse_negation(expr):
     # global constraints
     elif hasattr(expr, "decompose"):
         newexpr = copy.copy(expr)
-        # args are positive as we will negate the global, still check if no 'not' in its arguments
+        # args are positive as we will negate the global, still check if no 'not' in its arguments        
         newexpr.update_args(push_down_negation(expr.args, toplevel=False))
-        return ~newexpr
+        return newexpr.negate()
 
     elif is_bool(expr): # unlikely case with non-CPMpy True or False
         return ~BoolVal(expr)

cpmpy/transformations/normalize.py

@@ -227,7 +227,8 @@ def simplify_boolean(lst_of_expr, num_context=False):
                 if is_bool(res): # Result is a Boolean constant
                     newlist.append(int(res) if num_context else BoolVal(res))
                 else: # Result is an expression
-                    newlist.append(res)                    
+                    newlist.append(res)    
+
         elif isinstance(expr, (GlobalConstraint, GlobalFunction)):
             newargs = simplify_boolean(expr.args) # TODO: how to determine which are Bool/int?
             if any(a1 is not a2 for a1,a2 in zip(expr.args, newargs)):