What's the recommended way to convert a string to an array? I'm looking for something like:
template<class T, size_t N, class V>
std::array<T, N> to_array(const V& v)
{
assert(v.size() == N);
std::array<T, N> d;
std::copy(v.begin(), v.end(), d.data());
return d;
}
Does C++11 or Boost provide something like this? How do others do this? Seems silly having to copy/paste this function myself every time I need it in a project.
Simply calling:
std::copy(v.begin(), v.end(), d.data());
is The way to convert a string to the array. I don't see any advantage of wrapping this into a dedicated "utility" function.
In addition, unless the compiler optimizes it, the performance may degrade with your function: the data will be copied second time when returning the array.
That seems fine. There isn't such a thing in C++11, and I don't think there is one in Boost either. If you don't want to paste this all over the place, you can just put it in a header and #include that.
If you really only want convert string to an array, just use .c_str() (and work on char*). It isn't exactly array<> but may suit your needs.
That's fine, maybe with a minor modification in C++11.
template<class T, size_t N, class V>
std::array<T, N> to_array(const V& v)
{
assert(v.size() == N);
std::array<T, N> d;
using std::begin; using std::end;
std::copy( begin(v), end(v), begin(d) ); // this is the recommended way
return d;
}
That way, if you remove the assertion, this function would work even if v is a raw array.
using std::begin; using std::end; std::copy(begin(v),end(v),begin(d));
using std::begin; using std::end; makes the to_array truly generic. If you use std::begin(v) you're preventing your container T from overriding begin(). Bottom line, you need the extra line to let Koenig resolution do what it's supposed to do!It doesn't work with std::string, but if you're using a C string literal (char const *), C++20 introduces std::to_array for just this sort of thing:
std::array arr {"Hello, world!"};
