import java.util.function.Function;
import org.derive4j.Data;

@Data
interface Either<A, B> {

  <X> X match(Function<A, X> left, Function<B, X> right); 
    
  static void main(String[] args) {
    
    Either<Integer, String> l = Eithers.left(-1);
    Either<Integer, String> r = Eithers.right("Ok");

    Function<Either<Integer, String>, String> toString = Eithers.<Integer, String>
        cases()
        .left(String::valueOf)
        .right(Function.identity());

    int intValue = Eithers.
        caseOf(l)
        .left(Function.identity())
        .right(String::length);

    int intValue2 = r.match(left -> left, right -> right.length());
  }
}