Fixed type_to_string template for Unary and Binary cases to comply c++11 and higher. Added co_equal_fwd.hpp and got default values right. Replaced deprecated sprintf in toytime.

include/boost/icl/detail/co_equal_fwd.hpp

@@ -0,0 +1,47 @@
+#ifndef BOOST_ICL_DETAIL_CO_EQUAL_FWD_HPP_JOFA_20251205
+#define BOOST_ICL_DETAIL_CO_EQUAL_FWD_HPP_JOFA_20251205
+
+// Lightweight forward-declarations of co_equal overloads that match the real
+// SFINAE-enabled definitions. This avoids an unconstrained generic template
+// competing with the real overloads and producing ambiguous calls.
+//
+// Includes mirror the headers needed for the traits used in the enable_if
+// conditions. Adjust includes if your project places these traits elsewhere.
+
+#include <boost/icl/detail/design_config.hpp>
+#include <boost/icl/type_traits/is_combinable.hpp> // provides is_map, is_key_compare_equal, etc.
+#include <boost/mpl/not.hpp>
+#include <boost/mpl/and.hpp>
+#include <boost/utility/enable_if.hpp> // boost::enable_if
+
+namespace boost { namespace icl {
+
+// Overload used when both containers are maps and key-compare-equal:
+template<class Type, class CoType>
+typename boost::enable_if<
+    boost::mpl::and_<
+        is_key_compare_equal<Type, CoType>,
+        boost::mpl::and_< is_map<Type>, is_map<CoType> >
+    >,
+    bool
+>::type
+co_equal(typename Type::const_iterator left_,
+         typename CoType::const_iterator right_,
+         const Type* = 0, const CoType* = 0);
+
+// Overload used when key-compare-equal but not both maps
+template<class Type, class CoType>
+typename boost::enable_if<
+    boost::mpl::and_<
+        is_key_compare_equal<Type, CoType>,
+        boost::mpl::not_< boost::mpl::and_< is_map<Type>, is_map<CoType> > >
+    >,
+    bool
+>::type
+co_equal(typename Type::const_iterator,
+         typename CoType::const_iterator,
+         const Type* = 0, const CoType* = 0);
+
+}} // namespace boost::icl
+
+#endif // BOOST_ICL_DETAIL_CO_EQUAL_FWD_HPP_JOFA_20251205