Function eval

test/matchit/constexpr.cpp:23–31

template <typename Value>
constexpr auto eval(Value &&input)
{
  return match(input)(
      // clang-format off
        pattern | ds('/', 1, 1) = expr(1),
        pattern | ds('/', 0, _) = expr(0),
        pattern | _             = expr(-1));
  // clang-format on
}

static_assert(eval(std::make_tuple('/', 0, 5)) == 0);