Expose access to action map for a strategy

This provides a crude interface to the mapping from infoset to action
as part of a strategy for an extensive game.

A function `.action()` has been added in Python as well.

This is not a final polished interface for this information, just a starter
to enable work on issue 440.

Author: tturocy

src/games/game.cc

@@ -46,6 +46,26 @@ GameOutcomeRep::GameOutcomeRep(GameRep *p_game, int p_number) : m_game(p_game),
   }
 }
 
+//========================================================================
+//                      class GameStrategyRep
+//========================================================================
+
+GameAction GameStrategyRep::GetAction(const GameInfoset &p_infoset) const
+{
+  if (p_infoset->GetPlayer() != m_player) {
+    throw MismatchException();
+  }
+  int action = m_behav[p_infoset->GetNumber()];
+  return (action) ? *std::next(p_infoset->GetActions().cbegin(), action - 1) : nullptr;
+}
+
+void GameStrategyRep::DeleteStrategy()
+{
+  if (m_player->GetGame()->IsTree()) {
+    throw UndefinedException();
+  }
+}
+
 //========================================================================
 //                       class GamePlayerRep
 //========================================================================

src/games/game.h

@@ -358,6 +358,12 @@ class GameStrategyRep : public GameObject {
   GamePlayer GetPlayer() const;
   /// Returns the index of the strategy for its player
   int GetNumber() const { return m_number; }
+
+  /// Returns the action specified by the strategy at the information set
+  GameAction GetAction(const GameInfoset &) const;
+
+  /// Remove this strategy from the game
+  void DeleteStrategy();
   //@}
 };
 

src/pygambit/gambit.pxd

@@ -97,6 +97,8 @@ cdef extern from "games/game.h":
         c_GamePlayer GetPlayer() except +
         string GetLabel() except +
         void SetLabel(string) except +
+        c_GameAction GetAction(c_GameInfoset) except +
+        void DeleteStrategy() except +
 
     cdef cppclass c_GameActionRep "GameActionRep":
         int GetNumber() except +

src/pygambit/strategy.pxi

@@ -73,3 +73,6 @@ class Strategy:
     def number(self) -> int:
         """The number of the strategy."""
         return self.strategy.deref().GetNumber() - 1
+
+    def action(self, infoset: Infoset) -> Action:
+        return Action.wrap(self.strategy.deref().GetAction(infoset.infoset))