Range-based for over pair list

Question

Say, I want to iterate a number of pairs defined inline. Is there a shorter way to write:

for(auto pair : std::initializer_list<std::pair<int,int>>{{1,2}, {3,4}})
    // ...

?

Answer 1

Just specify the first element is a pair. The rest will be deduced automatically:

for(auto& pair : {std::pair<int,int>{1,2}, {3,4}})
  ;

The braced enclosed initializer is deduced to be std::initalizer_list, and the first element being named a pair will require all elements to be an initalizer for a pair.

You tagged C++11, but for completeness, it can be even shorter in C++17:

for(auto& pair : {std::pair{1,2}, {3,4}})
  ;

Due to class template argument deduction. If you don't have that, than std::make_pair will do if you want to maintain the benefits of template argument deduction:

for(auto& pair : {std::make_pair(1,2), {3,4}})
  ;

Though ostensibly, it isn't as useful for code golfing as the C++17 version.

Answer 2

The good ol' type alias:

using pairlist = std::initializer_list<std::pair<int,int>>;

for(auto pair : pairlist{{1,2}, {3,4}})
{
    // stuff happens here
}