function_base.hpp:

- Remove safe_bool conversion and operator! from class function_base

function_template.hpp:
  - Add safe_bool conversion and operator!
  - operator! returns bool, not safe_bool (Peter Dimov)

reference.html:
  - Document above change


[SVN r15356]

include/boost/function/function_template.hpp

@@ -419,6 +419,25 @@ namespace boost {
       invoker = 0;
     }
 
+#if (defined __SUNPRO_CC) && (__SUNPRO_CC <= 0x530) && !(defined BOOST_NO_COMPILER_CONFIG)
+    // Sun C++ 5.3 can't handle the safe_bool idiom, so don't use it
+    operator bool () const { return !this->empty(); }
+#else
+  private:
+    struct dummy {
+      void nonnull() {};
+    };
+
+    typedef void (dummy::*safe_bool)();
+
+  public:
+    operator safe_bool () const 
+      { return (this->empty())? 0 : &dummy::nonnull; }
+
+    bool operator!() const
+      { return this->empty(); }
+#endif
+
   private:
     void assign_to_own(const BOOST_FUNCTION_FUNCTION& f)
     {