In C++14, how do I initialize a global constexpr std::array of std::pair containing text strings? The following doesn't work:
#include <array>
constexpr std::array<std::pair<int, const char[]>, 3> strings = {
{0, "Int"},
{1, "Float"},
{2, "Bool"}};
You are almost there. First of all, the char const[] type needs to be a pointer instead, because it is an incomplete type, that may not be held in a std::pair. And secondly, you are missing a pair of braces. The correct declaration will look like this:
constexpr std::array<std::pair<int, const char*>, 3> strings = {{
{0, "Int"},
{1, "Float"},
{2, "Bool"},
}};
The extra braces are required because std::array is an aggregate holding a raw C array, and so we need the braces mentioned explicitly so that {0, "Int"} is not taken erroneously as the initializer for the inner array object.
std::array<std::string,2> s = {"Hi","Hello"}; and std::array<std::string,2> s = {{"Hi, "Hello"}}; are both deemed identical after C++14 (in case of non-constexpr array). Why doesn't the same rule apply here ?
std::array<std::string, 2> s={"hi", "hello"};, std::array<std::string, 2> s={{"hi", "hello"}};, std::array<std::string, 2> s={{"hi"}, {"hello"}};, std::array<std::string, 2> s={{{"hi"}, {"hello"}}}; to see the difference. Thanks for the explanation.An alternative in C++20 is to use std::to_array which allows you to create an array where you don't need to specify the size up front.
constexpr auto strings = std::to_array<std::pair<int, const char*>>({
{0, "Int"},
{1, "Float"},
{2, "Bool"},
});
std::to_array is of questionable benefit here. If you're making your answer specific to C++20, you should probably also use std::string_view instead of const char*. Having the size information can be a big performance boost in some cases.