Which greedy initializer-list examples are lurking in the Standard Library?

Question

Since C++11, the Standard Library containers and std::string have constructors taking an initializer-list. This constructor takes precedence over other construc

Answer 1

I assume, with your examples for std::vector<int> and std::string you meant to also cover the other containers, e.g., std::list<int>, std::deque<int>, etc. which have the same problem, obviously, as std::vector<int>. Likewise, the int isn't the only type as it also applies to char, short, long and their unsigned version (possibly a few other integral types, too).

I think there is also std::valarray<T> but I'm not sure if T is allowed to be integral type. Actually, I think these have different semantics:

std::valarray<double>(0.0, 3);
std::valarray<double>{0.0, 3};

There are a few other standard C++ class templates which take an std::initializer_list<T> as argument but I don't think any of these has an overloaded constructor which would be used when using parenthesis instead of braces.

Answer 2

Just searching for the occurence of initializer_list.

• All sequences, they are have the constructors like that of vector:

  • deque
  • dynarray
  • forward_list
  • list
  • vector

• valarray

• basic_string

• Unordered collections, there is a constructor which takes an integer to determine the initial bucket count.

  • unordered_set
  • unordered_multiset

I think that's all of it.

#include <unordered_set>
#include <iostream>

int main() {
    std::unordered_set<int> f (3);
    std::unordered_set<int> g {3};
    std::cout << f.size() << "/" << g.size() << std::endl; // prints 0/1.
}