class defined in function

Asked Dec 05 '12 at 18:33

Active Dec 05 '12 at 18:44

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Possible Duplicate:
Using local classes with STL algorithms

I'm trying to pass a locally defined function object to STL functions and it does not work. Where in the world is it declared that this ought not to be possible ? That looks rather appealing to me !

Here's code that fails:

int main() {
  std::vector<int> v;
  struct gen { int operator()(){return 4;} };
  std::cout<<gen()()<<std::endl; // works
  std::generate_n(std::back_inserter(v),4,gen()); // fails
}

Incidentally, the following does work, not because gen_s is a struct, but because gen_s::gen is a static function. This is not so cool because what's the use of a stateless generator ?

std:vector<int> v;
struct gen_s { static int gen() { return 4; };
std::generate_n(std::back_inserter(v),5,gen_s::gen);

So, what about locally defined function objects ?

edited May 23 '17 at 12:21

Community

asked Dec 05 '12 at 18:33

Gzorg

2

I think you meant `std::generate_n` instead of `std::generate` in the first piece of code. – prazuber Dec 05 '12 at 18:39
Local classes as template parameters are allowed in C++11, but not in earlier versions. – Bo Persson Dec 05 '12 at 18:42
@NPE Yes, I did a quick search with other keywords but didn't see this one. The answers it there. – Gzorg Dec 05 '12 at 18:44
By failing, I mean that it does not compile. – Gzorg Dec 05 '12 at 18:46

class defined in function

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