twaalgos: more doxygen comments

* spot/twaalgos/product.hh, spot/twaalgos/remfin.hh,
spot/twaalgos/sum.hh, spot/twaalgos/totgba.hh: Improve documentation.

spot/twaalgos/product.hh

@@ -26,24 +26,80 @@
 
 namespace spot
 {
-  // The tgba constructed by product() below contain property named
-  // "product-states" with type product_states.
+  /// \brief Automata constructed by product() contain a property
+  /// named "product-states" with this type
   typedef std::vector<std::pair<unsigned, unsigned>> product_states;
 
+  /// \ingroup twa_algorithms
+  /// \brief Intersect two automata using a synchronous product
+  ///
+  /// The resulting automaton will accept the intersection of both
+  /// languages and have an acceptance condition that is the
+  /// conjunction of the acceptance conditions of the two input
+  /// automata.
+  ///
+  /// The algorithm also defines a named property called
+  /// "product-states" with type spot::product_states.  This stores
+  /// the pair of original state numbers associated to each state of
+  /// the product.
   SPOT_API
   twa_graph_ptr product(const const_twa_graph_ptr& left,
                         const const_twa_graph_ptr& right);
 
+  /// \ingroup twa_algorithms
+  /// \brief Intersect two automata using a synchronous product
+  ///
+  /// These variant allow changing the initial state of both automata
+  /// in case you want to start the product at a different place.
+  ///
+  /// The resulting automaton will accept the intersection of the
+  /// languages recognized by each input automaton (with its initial
+  /// state changed) and have an acceptance condition that is the
+  /// conjunction of the acceptance conditions of the two input
+  /// automata.
+  ///
+  /// The algorithm also defines a named property called
+  /// "product-states" with type spot::product_states.  This stores
+  /// the pair of original state numbers associated to each state of
+  /// the product.
   SPOT_API
   twa_graph_ptr product(const const_twa_graph_ptr& left,
                         const const_twa_graph_ptr& right,
                         unsigned left_state,
                         unsigned right_state);
 
+  /// \ingroup twa_algorithms
+  /// \brief Sum two automata using a synchronous product
+  ///
+  /// The resulting automaton will accept the union of both
+  /// languages and have an acceptance condition that is the
+  /// disjunction of the acceptance conditions of the two input
+  /// automata.
+  ///
+  /// The algorithm also defines a named property called
+  /// "product-states" with type spot::product_states.  This stores
+  /// the pair of original state numbers associated to each state of
+  /// the product.
   SPOT_API
   twa_graph_ptr product_or(const const_twa_graph_ptr& left,
                            const const_twa_graph_ptr& right);
 
+  /// \ingroup twa_algorithms
+  /// \brief Sum two automata using a synchronous product
+  ///
+  /// These variant allow changing the initial state of both automata
+  /// in case you want to start the product at a different place.
+  ///
+  /// The resulting automaton will accept the sum of the languages
+  /// recognized by each input automaton (with its initial state
+  /// changed) and have an acceptance condition that is the
+  /// disjunction of the acceptance conditions of the two input
+  /// automata.
+  ///
+  /// The algorithm also defines a named property called
+  /// "product-states" with type spot::product_states.  This stores
+  /// the pair of original state numbers associated to each state of
+  /// the product.
   SPOT_API
   twa_graph_ptr product_or(const const_twa_graph_ptr& left,
                            const const_twa_graph_ptr& right,

spot/twaalgos/remfin.hh

@@ -23,11 +23,12 @@
 
 namespace spot
 {
-  /// \brief Convert a state-based Rabin automaton to Büchi automaton,
-  /// preserving determinism when possible.
+  /// \ingroup twa_algorithms
+  /// \brief Convert a Rabin automaton to Büchi automaton, preserving
+  /// determinism when possible.
   ///
-  /// Return nullptr if the input is not a Rabin automaton, or is not
-  /// state-based.
+  /// Return nullptr if the input is not a Rabin (or Rabin-like)
+  /// automaton.
   ///
   /// This essentially applies the algorithm from "Deterministic
   /// ω-automata vis-a-vis Deterministic Büchi Automata", S. Krishnan,
@@ -39,7 +40,13 @@ namespace spot
   SPOT_API twa_graph_ptr
   rabin_to_buchi_maybe(const const_twa_graph_ptr& aut);
 
+  /// \ingroup twa_algorithms
   /// \brief Rewrite an automaton without Fin acceptance.
+  ///
+  /// This algorithm dispatches between many strategies.  It has
+  /// dedicated algorithms for weak automata, automata with Rabin-like
+  /// acceptance, automata with Streett-like acceptance, and some
+  /// generic code that will work on any kind of acceptance condition.
   SPOT_API twa_graph_ptr
   remove_fin(const const_twa_graph_ptr& aut);
 }

spot/twaalgos/sum.hh

@@ -24,6 +24,7 @@
 
 namespace spot
 {
+  /// \ingroup twa_algorithms
   /// \brief Sum two twa into a new twa, performing the union of the two input
   /// automata.
   ///
@@ -34,6 +35,7 @@ namespace spot
   twa_graph_ptr sum(const const_twa_graph_ptr& left,
                     const const_twa_graph_ptr& right);
 
+  /// \ingroup twa_algorithms
   /// \brief Sum two twa into a new twa, performing the union of the two input
   /// automata.
   ///
@@ -48,6 +50,7 @@ namespace spot
                     unsigned left_state,
                     unsigned right_state);
 
+  /// \ingroup twa_algorithms
   /// \brief Sum two twa into a new twa, using a universal initial transition,
   /// performing the intersection of the two languages of the input automata.
   ///
@@ -58,6 +61,7 @@ namespace spot
   twa_graph_ptr sum_and(const const_twa_graph_ptr& left,
                         const const_twa_graph_ptr& right);
 
+  /// \ingroup twa_algorithms
   /// \brief Sum two twa into a new twa, using a universal initial transition,
   /// performing the intersection of the two languages of the input automata.
   ///

spot/twaalgos/totgba.hh

@@ -25,22 +25,35 @@
 
 namespace spot
 {
+  /// \ingroup twa_algorithms
   /// \brief Take an automaton with any acceptance condition and return
   /// an equivalent Generalized Büchi automaton.
+  ///
+  /// This dispatch between many algorithms.  If the input has Streett
+  /// (or Streett-like) acceptance,
+  /// spot::streett_to_generalized_buchi() is called right away and
+  /// produces a TGBA.  Otherwise, it calls spot::remove_in() which
+  /// returns a TBA.
   SPOT_API twa_graph_ptr
   to_generalized_buchi(const const_twa_graph_ptr& aut);
 
+  /// \ingroup twa_algorithms
   /// \brief Convert Streett acceptance into generalized Büchi
   /// acceptance.
   SPOT_API twa_graph_ptr
   streett_to_generalized_buchi(const const_twa_graph_ptr& in);
 
+  /// \ingroup twa_algorithms
   /// \brief Convert Streett acceptance into generalized Büchi
-  /// only if SPOT_STREET_CONF_MIN is set to a number of pairs
-  /// less than the number of pairs used by IN.
+  ///
+  /// This version only works SPOT_STREET_CONF_MIN is set to a number
+  /// of pairs less than the number of pairs used by \a in.  The
+  /// default is 3.  It returns nullptr of that condition is not met,
+  /// or if the input automaton does not have Streett-like acceptance.
   SPOT_API twa_graph_ptr
   streett_to_generalized_buchi_maybe(const const_twa_graph_ptr& in);
 
+  /// \ingroup twa_algorithms
   /// \brief Take an automaton with any acceptance condition and return
   /// an equivalent Generalized Rabin automaton.
   ///
@@ -55,6 +68,7 @@ namespace spot
   to_generalized_rabin(const const_twa_graph_ptr& aut,
                        bool share_inf = false);
 
+  /// \ingroup twa_algorithms
   /// \brief Take an automaton with any acceptance condition and return
   /// an equivalent Generalized Streett automaton.
   ///