* src/ltlast/atomic_prop.hh, src/ltlast/binop.hh,

src/ltlast/constant.hh, src/ltlast/formula.hh,
src/ltlast/multop.hh, src/ltlast/unop.hh, src/ltlast/visitor.hh,
src/ltlenv/defaultenv.hh, src/ltlenv/environment.hh,
src/ltlparse/public.hh, src/ltlvisit/clone.hh,
src/ltlvisit/dotty.hh, src/ltlvisit/dump.hh,
src/ltlvisit/equals.hh, src/ltlvisit/lunabbrev.hh,
src/ltlvisit/nenoform.hh, src/ltlvisit/tunabbrev.hh: Add
Doxygen comments.
* src/visitor.hh: Do not use const_sel.  This clarify
the code and helps Doxygen.

src/ltlenv/defaultenv.hh

@@ -9,13 +9,19 @@ namespace spot
   namespace ltl
   {
 
+    /// \brief A laxist environment.
+    ///
+    /// The environment recognize all atomic propositions.
+    ///
+    /// This is a singleton.  Use default_environment::instance()
+    /// to obtain the instance.
     class default_environment : public environment
     {
     public:
       virtual formula* require(const std::string& prop_str);
       virtual const std::string& name();
 
-      /* This class is a singleton.  */
+      /// Get the sole instance of spot::ltl::default_environment.
       static default_environment& instance();
     protected:
       default_environment();

src/ltlenv/environment.hh

@@ -9,20 +9,32 @@ namespace spot
   namespace ltl
   {
 
+    /// An environment that describe atomic propositions.
     class environment
     {
     public:
-      // Check whether the environment contains the atomic proposition
-      // described by prop_str.
-      // Note this is NOT a const method.  Some environment will
-      // "create" the atomic proposition when asked.
-      // We return a formula instead of an atomic_prop, because this
-      // will allow nifty tricks (e.g., we could name formulae in an
-      // environment, and let the parser build a larger tree from
-      // these).
+      /// \brief Obtain the formula associated to \a prop_str
+      ///
+      /// Usually \a prop_str, is the name of an atomic proposition,
+      /// a spot::ltl::require simply returns the associated 
+      /// spot::ltl::atomic_prop.
+      ///
+      /// Note this is not a \c const method.  Some environment will
+      /// "create" the atomic proposition when asked.
+      ///
+      /// We return a spot::ltl::formula instead of an 
+      /// spot::ltl::atomic_prop, because this
+      /// will allow nifty tricks (e.g., we could name formulae in an
+      /// environment, and let the parser build a larger tree from
+      /// these).
+      ///
+      /// \return 0 iff \a prop_str is not part of the environment,
+      ///   or the associated spot::ltl::formula otherwise.
       virtual formula* require(const std::string& prop_str) = 0; 
 
+      /// Get the name of the environment.
       virtual const std::string& name() = 0;
+
       // FIXME: More functions will be needed later, but
       // it's enough for now.
     };