* configure.ac: Output src/ltlenv/Makefile.

* src/ltlenv/Makefile.am, src/ltlenv/defaultenv.cc,
src/ltlenv/defaultenv.hh, src/ltlenv/environment.hh: New files.
* src/ltlparse/public.hh (parse): Take an environment as third
argument.
* src/ltlparse/ltlparse.yy (ATOMIC_PROP, parse): Require the
atomic proposition via the environment.
* src/ltltest/readltl.cc (main): Adjust the call to parse().
* src/ltltest/Makefile.am (LDADD): Add ../ltlenv/libltlenv.a.

src/ltlenv/.cvsignore

@@ -0,0 +1,4 @@
+.deps
+Makefile
+Makefile.in
+libltlenv.a

src/ltlenv/Makefile.am

@@ -0,0 +1,8 @@
+AM_CPPFLAGS = -I$(srcdir)/..
+AM_CXXFLAGS = $(WARNING_CXXFLAGS)
+
+lib_LIBRARIES = libltlenv.a
+libltlenv_a_SOURCES = \
+  defaultenv.cc \
+  defaultenv.hh \
+  environment.hh

src/ltlenv/defaultenv.cc

@@ -0,0 +1,33 @@
+#include "defaultenv.hh"
+
+namespace spot
+{
+  namespace ltl
+  {
+
+    atomic_prop*
+    default_environment::require(const std::string& s)
+    {
+      return new atomic_prop(s);
+    }
+
+    const std::string&
+    default_environment::name()
+    {
+      static std::string name("default environment");
+      return name;
+    }
+
+    default_environment::default_environment()
+    {
+    }
+
+    default_environment& 
+    default_environment::instance()
+    {
+      static default_environment* singleton = new default_environment();
+      return *singleton;
+    }
+
+  }
+}

src/ltlenv/defaultenv.hh

@@ -0,0 +1,26 @@
+#ifndef SPOT_LTLENV_DEFAULT_ENVIRONMENT_HH
+# define SPOT_LTLENV_DEFAULT_ENVIRONMENT_HH
+
+# include "environment.hh"
+
+namespace spot
+{
+  namespace ltl
+  {
+
+    class default_environment : public environment
+    {
+    public:
+      virtual atomic_prop* require(const std::string& prop_str);
+      virtual const std::string& name();
+
+      /* This class is a singleton.  */
+      static default_environment& instance();
+    protected:
+      default_environment();
+    };
+
+  }
+}
+
+#endif // SPOT_LTLENV_DEFAULT_ENVIRONMENT_HH

src/ltlenv/environment.hh

@@ -0,0 +1,29 @@
+#ifndef SPOT_LTLENV_ENVIRONMENT_HH
+# define SPOT_LTLENV_ENVIRONMENT_HH
+
+# include "ltlast/atomic_prop.hh"
+# include <string>
+
+namespace spot
+{
+  namespace ltl
+  {
+
+    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.
+      virtual atomic_prop* require(const std::string& prop_str) = 0; 
+
+      virtual const std::string& name() = 0;
+      // FIXME: More functions will be needed later, but
+      // it's enough for now.
+    };
+
+  }
+}
+
+#endif // SPOT_LTLENV_ENVIRONMENT_HH