trival: prefer a global operator== relying on implicit conversion

Hopefully fixes #359.

* spot/misc/trival.hh: Declare a global operator==(trival,trival) that
replace the specialized operator==(bool,trival), and the in class
trival::operator(trival), thanks to the implicit construction from
bool to trival.  Make the repr_t/value_t constructor explicit, are
those are mostly internal to the library and may cause conflicts.
* spot/twa/twa.hh: Adjust to construct trival explicitly.
* python/spot/impl.i: Since Swig/Python does not support global
comparison operators, implement a member version, supporting
only __eq__(trival,bool) as before.
* tests/python/setacc.py: Adjust erroneous code.
* tests/python/trival.py: Add test cases.

python/spot/impl.i

@@ -681,6 +681,16 @@ def state_is_accepting(self, src) -> "bool":
   {
     return *self || other;
   }
+
+  bool __eq__(spot::trival other)
+  {
+    return self->val() == other.val();
+  }
+
+  bool __ne__(spot::trival other)
+  {
+    return self->val() != other.val();
+  }
 }
 
 

spot/misc/trival.hh

@@ -1,6 +1,6 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2016 Laboratoire de Recherche et Developpement de
-// l'Epita (LRDE).
+// Copyright (C) 2016, 2018 Laboratoire de Recherche et Developpement
+// de l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
 //
@@ -50,12 +50,16 @@ namespace spot
     {
     }
 
-    trival(repr_t v)
+#ifndef SWIG
+    // This is needed internally by Spot to work around the bitfield
+    // issue mentioned earlier, it makes no sense to use it in Python.
+    static trival from_repr_t(repr_t v)
     {
-      val_ = static_cast<value_t>(v);
+      return trival(static_cast<value_t>(v));
     }
+#endif
 
-    constexpr trival(value_t v)
+    constexpr explicit trival(value_t v)
       : val_(v)
     {
     }
@@ -86,16 +90,6 @@ namespace spot
       return val_ == no_value;
     }
 
-    constexpr bool operator==(trival o) const
-    {
-      return val_ == o.val_;
-    }
-
-    constexpr bool operator!=(trival o) const
-    {
-      return val_ != o.val_;
-    }
-
     constexpr value_t val() const
     {
       return val_;
@@ -118,15 +112,24 @@ namespace spot
     }
   };
 
-  constexpr bool operator==(bool a, trival b)
+  // We prefer a global version of the operator so that the left
+  // argument can be promoted (think "bool == trival" being promoted
+  // to "trival == trival").  However Swig's generated Python bindings
+  // cannot deal with operators in the global namespace, so we use an
+  // in-class version (coded in impl.i) in this case.  This will fail
+  // on a "bool == trival" comparison in Python, but we usually write
+  // "trival == bool" and that works.
+#ifndef SWIG
+  constexpr bool operator==(trival a, trival b)
   {
-    return b == trival(a);
+    return a.val() == b.val();
   }
 
-  constexpr bool operator!=(bool a, trival b)
+  constexpr bool operator!=(trival a, trival b)
   {
-    return b != trival(a);
+    return !(a == b);
   }
+#endif
 
   constexpr trival operator&&(trival a, trival b)
   {

spot/twa/twa.hh

@@ -1203,8 +1203,8 @@ namespace spot
     trival prop_state_acc() const
     {
       if (num_sets() == 0)
-        return true;
-      return is.state_based_acc;
+        return trival(true);
+      return trival::from_repr_t(is.state_based_acc);
     }
 
     /// \brief Set the state-based-acceptance property.
@@ -1235,7 +1235,7 @@ namespace spot
     /// \see prop_terminal()
     trival prop_inherently_weak() const
     {
-      return is.inherently_weak;
+      return trival::from_repr_t(is.inherently_weak);
     }
 
     /// \brief Set the "inherently weak" property.
@@ -1265,7 +1265,7 @@ namespace spot
     /// \see prop_inherently_weak()
     trival prop_terminal() const
     {
-      return is.terminal;
+      return trival::from_repr_t(is.terminal);
     }
 
     /// \brief Set the terminal property.
@@ -1291,7 +1291,7 @@ namespace spot
     /// \see prop_inherently_weak()
     trival prop_weak() const
     {
-      return is.weak;
+      return trival::from_repr_t(is.weak);
     }
 
     /// \brief Set the weak property.
@@ -1321,7 +1321,7 @@ namespace spot
     /// \see prop_weak()
     trival prop_very_weak() const
     {
-      return is.very_weak;
+      return trival::from_repr_t(is.very_weak);
     }
 
     /// \brief Set the very-weak property.
@@ -1352,7 +1352,7 @@ namespace spot
     /// \see is_complete()
     trival prop_complete() const
     {
-      return is.complete;
+      return trival::from_repr_t(is.complete);
     }
 
     /// \brief Set the complete property.
@@ -1376,7 +1376,7 @@ namespace spot
     /// \see is_universal()
     trival prop_universal() const
     {
-      return is.universal;
+      return trival::from_repr_t(is.universal);
     }
 
     /// \brief Set the universal property.
@@ -1427,7 +1427,7 @@ namespace spot
     /// \see is_unambiguous()
     trival prop_unambiguous() const
     {
-      return is.unambiguous;
+      return trival::from_repr_t(is.unambiguous);
     }
 
     /// \brief Set the unambiguous property
@@ -1457,7 +1457,7 @@ namespace spot
     /// \see is_semi_deterministic()
     trival prop_semi_deterministic() const
     {
-      return is.semi_deterministic;
+      return trival::from_repr_t(is.semi_deterministic);
     }
 
     /// \brief Set the semi-deterministic property
@@ -1487,7 +1487,7 @@ namespace spot
     /// \see is_stutter_invariant
     trival prop_stutter_invariant() const
     {
-      return is.stutter_invariant;
+      return trival::from_repr_t(is.stutter_invariant);
     }
 
     /// \brief Set the stutter-invariant property

tests/python/setacc.py

@@ -1,6 +1,6 @@
 #!/usr/bin/python3
 # -*- mode: python; coding: utf-8 -*-
-# Copyright (C) 2016 Laboratoire de Recherche et Développement de
+# Copyright (C) 2016, 2018 Laboratoire de Recherche et Développement de
 # l'EPITA.
 #
 # This file is part of Spot, a model checking library.
@@ -22,5 +22,6 @@
 import spot
 a = spot.make_twa_graph(spot._bdd_dict)
 a.set_acceptance(0, spot.acc_code("t"))
+assert(a.prop_state_acc() == True);
 a.set_acceptance(1, spot.acc_code("Fin(0)"))
-assert(a.prop_state_acc() == 0);
+assert(a.prop_state_acc() == spot.trival.maybe());

tests/python/trival.py

@@ -1,5 +1,5 @@
 # -*- mode: python; coding: utf-8 -*-
-# Copyright (C) 2016  Laboratoire de Recherche et Développement
+# Copyright (C) 2016, 2018  Laboratoire de Recherche et Développement
 # de l'Epita
 #
 # This file is part of Spot, a model checking library.
@@ -26,11 +26,16 @@ v4 = spot.trival_maybe()
 assert v1 != v2
 assert v1 != v3
 assert v2 != v3
+assert v2 == spot.trival(spot.trival.no_value)
+assert v2 != spot.trival(spot.trival.yes_value)
 assert v4 != v2
 assert v4 != v3
 assert v2 == False
 assert True == v3
+assert v2 != True
+assert False != v3
 assert v4 == spot.trival_maybe()
+assert v4 == spot.trival(spot.trival.maybe_value)
 assert v3
 assert -v2
 assert not -v1