54d34a1b   
   From: daniel.kruegler@googlemail.com   
      
   { This thread has turned into a debugging effort of a specific piece   
      of code, which limits its relevance to the general C++ community.   
      Please keep that in mind when replying -mod }   
      
   Am 19.05.2012 10:28, schrieb Mark Summerfield:   
   > I tried what you suggested but got the same errors.   
   >   
   > template   
   > struct identity { typedef T type; };   
   > template   
   > using NonDeduced = typename identity::type;   
   >   
   > template   
   > using Validator = std::function;   
   >   
   > template   
   > Validator   
   > makeSetValidator(const C&validItems,   
   >       NonDeduced  validate)   
   > {   
   >       return [=](const std::string s)->typename C::value_type{   
   >           const auto x = validate(s);   
   >           if (std::find(std::begin(validItems), std::end(validItems), x)   
   >               != std::end(validItems))   
   >               return x;   
   >           throw ValueError("Invalid item '" + s + "'");   
   >       };   
   > }   
   >   
   > template   
   > T validate(const std::string s) { ... }   
   >   
   > At the call site I tried:   
   >   
   > auto v = makeSetValidator(std::set{-4, 8, 31},   
   > validate);   
   > auto v = makeSetValidator(std::set{-4, 8, 31}, validate);   
   > auto v = makeSetValidator(std::set{-4, 8, 31}, validate);   
   > auto v = makeSetValidator(std::set{-4, 8, 31}, validate);   
   >   
   > None of which would compile.   
      
   The first and third form cannot possibly be well-formed for reasons   
   that I explained in my very first reply in this thread. The other   
   forms should work. Since you do not provide a complete program, but   
   only snippets there might be several reasons for the failure (include   
   that the compiler version you used cannot properly handle some of the   
   new C++11 constructs). Except from the lambda expression, it is easy   
   to make your code a fully C++03 compatible program like so:   
      
   #include    
   #include    
      
   template   
   struct identity { typedef T type; };   
      
   struct ValueError { ValueError(const std::string& what) {} };   
      
   template   
   struct function;   
      
   template   
   struct function   
   {   
       template   
       function(F){}   
   };   
      
   template   
   function   
   makeSetValidator(const C &validItems,   
          typename identity::type validate)   
   {   
       return function(validate);   
   }   
      
   template   
   T validate(const std::string s) { return T(); }   
      
   int main()   
   {   
       makeSetValidator(std::set(), validate);   
       makeSetValidator(std::set(), validate);   
   }   
      
   This compiles on every compiler I tested. I recommend to start with   
   this and to increase the functionality step-wise to the point where it   
   does no longer work, then try to isolate the actual problem.   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
      
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