Initialize unordered_map in the initializer list

Question

I'm trying to find a solution to what may be a very trivial problem. I would like to initialize my const unordered_map in the class initializer list. However I'm yet to find the syntax that the compiler (GCC 6.2.0) will accept. A code link is here.

#include <unordered_map>

class test {
 public:
    test()
      : map_({23, 1345}, {43, -8745}) {}

 private:
   const std::unordered_map<long, long> map_;
 };

Error:

main.cpp: In constructor 'test::test()':
main.cpp:6:36: error: no matching function for call to 'std::unordered_map<long int, long int>::unordered_map(<brace-enclosed initializer list>, <brace-enclosed initializer list>)'
  : map_({23, 1345}, {43, -8745}) {}
                                ^

Are the complex constants not allowed to be initialized in the initializer list? Or the syntax has to be different?

Answer 1

Use braces instead of the parentheses

class test {
 public:
    test()
      : map_{{23, 1345}, {43, -8745}} {}

 private:
   const std::unordered_map<long, long> map_;
 };