Preserve decimal payoffs in strategic forms when possible in GUI.

ChangeLog

@@ -18,6 +18,8 @@
 ### Changed
 - All long-running calculations are now done in a thread in the GUI process, rather than calling the
   command-line executables as external processes. (#990)
+- When displaying a strategic form, the graphical interface preserves decimal payoffs when those are
+  what are specified in the game, whenever possible.  (#867)
 
 ### Removed
 - Assigning to `Strategy.label` has been removed; use `Game.relabel_strategies`, which enforces

src/games/behavpure.cc

@@ -73,6 +73,29 @@ T PureBehaviorProfile::GetPayoff(const GameNode &p_node, const GamePlayer &p_pla
 template double PureBehaviorProfile::GetPayoff(const GameNode &, const GamePlayer &) const;
 template Rational PureBehaviorProfile::GetPayoff(const GameNode &, const GamePlayer &) const;
 
+GameOutcome PureBehaviorProfile::GetOutcome(const GameNode &p_start) const
+{
+  GameOutcome outcome;
+  GameNode node = p_start;
+  while (true) {
+    if (node->GetOutcome()) {
+      if (outcome) {
+        // More than one outcome-bearing node along this path; the combined
+        // payoff cannot be attributed to a single outcome's preserved text.
+        throw UndefinedException();
+      }
+      outcome = node->GetOutcome();
+    }
+    if (node->IsTerminal()) {
+      return outcome;
+    }
+    if (node->GetInfoset()->IsChanceInfoset()) {
+      throw UndefinedException();
+    }
+    node = node->GetChild(m_profile.at(node->GetInfoset()));
+  }
+}
+
 MixedBehaviorProfile<Rational> PureBehaviorProfile::ToMixedBehaviorProfile() const
 {
   MixedBehaviorProfile<Rational> temp(m_efg);

src/games/behavpure.h

@@ -62,6 +62,13 @@ class PureBehaviorProfile {
   /// Get the payoff to the player, conditional on reaching a node
   template <class T> T GetPayoff(const GameNode &, const GamePlayer &) const;
 
+  /// Get the outcome that results from the profile, provided this can be
+  /// determined without resolving a chance move and without combining more
+  /// than one outcome along the induced path; throws UndefinedException otherwise.
+  GameOutcome GetOutcome() const { return GetOutcome(m_efg->GetRoot()); }
+  /// Get the outcome that results from the profile, conditional on reaching a node
+  GameOutcome GetOutcome(const GameNode &) const;
+
   /// Convert to a mixed behavior representation
   MixedBehaviorProfile<Rational> ToMixedBehaviorProfile() const;
   //@}

src/games/gametree.cc

@@ -1921,9 +1921,25 @@ class TreePureStrategyProfileRep : public PureStrategyProfileRep {
     return std::make_shared<TreePureStrategyProfileRep>(*this);
   }
 
+  /// Build the behavior profile induced by this pure strategy profile
+  PureBehaviorProfile GetBehaviorProfile() const
+  {
+    PureBehaviorProfile behav(m_game);
+    for (const auto &player : m_game->GetPlayers()) {
+      for (const auto &infoset : player->GetInfosets()) {
+        try {
+          behav.SetAction(infoset->GetAction(GetStrategy(player)->m_behav.at(infoset.get())));
+        }
+        catch (std::out_of_range &) {
+        }
+      }
+    }
+    return behav;
+  }
+
 public:
   TreePureStrategyProfileRep(const Game &p_game) : PureStrategyProfileRep(p_game) {}
-  GameOutcome GetOutcome() const override { throw UndefinedException(); }
+  GameOutcome GetOutcome() const override;
   void SetOutcome(GameOutcome p_outcome) override { throw UndefinedException(); }
   Rational GetPayoff(const GamePlayer &) const override;
   Rational GetStrategyValue(const GameStrategy &) const override;
@@ -1944,19 +1960,14 @@ PureStrategyProfile GameTreeRep::NewPureStrategyProfile() const
 //       TreePureStrategyProfileRep: Data access and manipulation
 //------------------------------------------------------------------------
 
+GameOutcome TreePureStrategyProfileRep::GetOutcome() const
+{
+  return GetBehaviorProfile().GetOutcome();
+}
+
 Rational TreePureStrategyProfileRep::GetPayoff(const GamePlayer &p_player) const
 {
-  PureBehaviorProfile behav(m_game);
-  for (const auto &player : m_game->GetPlayers()) {
-    for (const auto &infoset : player->GetInfosets()) {
-      try {
-        behav.SetAction(infoset->GetAction(GetStrategy(player)->m_behav.at(infoset.get())));
-      }
-      catch (std::out_of_range &) {
-      }
-    }
-  }
-  return behav.GetPayoff<Rational>(p_player);
+  return GetBehaviorProfile().GetPayoff<Rational>(p_player);
 }
 
 Rational TreePureStrategyProfileRep::GetStrategyValue(const GameStrategy &p_strategy) const

src/gui/nfgtable.cc

@@ -1010,8 +1010,16 @@ class PayoffTable final : public wxGridTableBase {
 wxString PayoffTable::GetValue(int row, int col)
 {
   const PureStrategyProfile profile = m_table->GetPayoffProfile(row, col);
-  auto player = m_table->GetPayoffPlayer(col);
-  return wxString::FromUTF8(lexical_cast<std::string>(profile->GetPayoff(player)));
+  const auto player = m_table->GetPayoffPlayer(col);
+  try {
+    if (const auto outcome = profile->GetOutcome()) {
+      return wxString::FromUTF8(outcome->GetPayoff<std::string>(player));
+    }
+    return wxString::FromUTF8("0");
+  }
+  catch (const UndefinedException &) {
+    return wxString::FromUTF8(lexical_cast<std::string>(profile->GetPayoff(player)));
+  }
 }
 
 void PayoffTable::SetValue(int row, int col, const wxString &value)