Extracting scanned value is cumbersome.

[hellokartikey]

The current API for extracting the scanned result is very cumbersome (IMO).

Sometimes it is better to return a fallback value when scan fails.

  ...
  auto number = scn::input<int>("{}").value_or(42);
  ...

The current way of achieving this is unnecessarily long.

  ...
  int number; // Have an uninitialized variable
  if (auto result = scn::input<int>("{}"); result) {
    number = result->value();
  else {
    number = 42;
  }
  ...

or

  ...
  int number = scn::input<int>("{}").value().value(); // Could throw and no fallback value
  ...

Having a scn::scan_result inside a std::expected can be somewhat inconvenient. Maybe having a single result type would be better?