fix a problem with formatting arbitrary types; reneable the broken tests

src/lib/format.hpp

@@ -39,6 +39,7 @@
 #include <string>
 #include <cstring>
 #include <typeinfo>
+#include <boost/lexical_cast.hpp>
 #include <boost/utility/enable_if.hpp>
 
 
@@ -46,6 +47,7 @@
 namespace util {
   
   using lumiera::typelist::can_ToString;
+  using lumiera::typelist::can_lexical2string;
   using lumiera::Symbol;
   using boost::enable_if;
   using boost::disable_if;
@@ -70,11 +72,36 @@ namespace util {
     {
       return "";
     }
+    
+    
+    
+    template<typename X>
+    inline string
+    invoke_indirect2string (     typename enable_if< can_lexical2string<X>,
+                            X >::type const& val)
+    {
+      try        { return boost::lexical_cast<string> (val); }
+      catch(...) { return ""; }
+    }
+    
+    template<typename X>
+    inline string
+    invoke_indirect2string (     typename disable_if< can_lexical2string<X>,
+                            X >::type const&)
+    {
+      return "";
+    }
   }
   
   
   
-  /** try to get an object converted to string */
+  /** try to get an object converted to string.
+   *  An custom/standard conversion to string is used,
+   *  if applicable; otherwise, some standard types can be
+   *  converted by a lexical_cast (based on operator<< ).
+   *  Otherwise, either the fallback string is used, or just
+   *  a string denoting the (mangled) type.
+   */
   template<typename TY>
   inline string
   str ( TY const& val
@@ -86,8 +113,17 @@ namespace util {
       return string(prefix) + invoke_2string<TY>(val);
     
     else
-      return fallback? fallback
-                     : tyStr(val);
+      {
+        if (can_lexical2string<TY>::value)
+          {
+            string res (invoke_indirect2string<TY> (val));
+            if ("" != res)
+              return string(prefix) + res;
+          }
+      
+        return fallback? fallback
+                       : tyStr(val);
+      }
   }
   
   

src/lib/meta/trait.hpp

@@ -28,11 +28,17 @@
 #include "lib/meta/util.hpp"
 
 #include <boost/type_traits/is_convertible.hpp>
+#include <boost/type_traits/is_arithmetic.hpp>
+#include <boost/utility/enable_if.hpp>
 #include <string>
 
   
 namespace lumiera {
 namespace typelist {
+
+  using boost::enable_if;
+  using boost::is_arithmetic;
+  
   
   /** Trait template for detecting if a type can be converted to string.
    *  For example, this allows to write specialisations with the help of
@@ -46,6 +52,24 @@ namespace typelist {
     };
   
   
+  /** Trait template for guarding \c lexical_cast<..> expressions.
+   *  Such an expression won't even compile for some types, because of
+   *  missing or ambiguous output operator(s).
+   *  Ideally, there would be some automatic detection (relying on the
+   *  existence of an operator<< for the given type. But I couldn't make
+   *  this work, so I fell back on just declaring types which are known
+   *  to work with lexical_cast to string
+   *  @note this compile-time trait can't predict if such an conversion
+   *        to string will be successful at runtime; indeed it may throw,
+   *        so you should additionally guard the invocation with try-catch!
+   */
+  template<typename X>
+  struct can_lexical2string
+    {
+      enum { value = is_arithmetic<X>::value
+           };
+    };
+  
   
 }} // namespace lumiera::typelist
 #endif

tests/40components.tests

@@ -240,6 +240,9 @@ out: «..util.test.Reticent.»
 out: <no comment>
 out: ^hey Joe!
 out: ^he says: hey Joe!
+out: ^the truth: 0
+out: ^just a number: 1.234e\+56
+out: ^12345X
 return: 0
 END
 

tests/45controller.tests

@@ -7,7 +7,7 @@ PLANNED "CommandBasic_test" CommandBasic_test <<END
 END
 
 
-PLANNED "Argument & Memento handling" CommandArgument_test <<END
+TEST "Argument & Memento handling" CommandArgument_test <<END
 out: Command-State. arguments=unbound, ·noUNDO·.
 out: capture state...
 out: Command-State. arguments=Closure\(\), ·noUNDO·.
@@ -35,7 +35,7 @@ out: RESET...undoIt\(time=00:..:....00\)----memento-:START...doIt\( Time=00:..:.
 END
 
 
-PLANNED "Command functor and UNDO functor" CommandMutation_test <<END
+TEST "Command functor and UNDO functor" CommandMutation_test <<END
 out: Mutation\(untied\)
 out: param values: Closure\(23\)
 out: Mutation\(Closure\(23\)\)

tests/lib/format-helper-test.cpp

@@ -75,6 +75,10 @@ namespace test {
           
           cout << str (chatterer) << endl;
           cout << str (chatterer, "he says: ", "<no comment>") << endl;
+          
+          cout << str (false, "the truth: ") << endl;
+          cout << str (12.34e55, "just a number: ") << endl;
+          cout << str (short(12)) << str (345L) << str ('X') << endl;
         }