Initializer list in user-defined literal parameter

Question

I don't know if it's possible but I want to do stuff like

int someval = 1;
if({1,2,3,4}_v.contains(someval ))

but when I try to define literal as:

std::vector<int> operator"" _v ( std::initializer_list<int> t )
{
    return std::vector<int> (t);
}

to accept initializer list of ints I get

 error: 'std::vector<int> operator"" _v(std::initializer_list<int> t)' has invalid argument list

Is there a way to do this? What I really want is to finally be rid of stuff like

if(value == 1 || value ==2 || value == 3 ...

Having to write stuff like this is really annoying, because you'd expect syntax to be

if value in (value1, value2 ...) 

or something similar.

Answer 1

How about this:

#include <initializer_list>

template <typename T>
bool contains(std::initializer_list<T> const & il, T const & x)
{
    for (auto const & z : il) { if (z == x) return true; }
    return false;
}

Usage:

bool b = contains({1, 2, 3}, 5);  // false