either<TL, TR> method

Future<Either<TL, TR>> either<TL, TR>(
  1. TL fnL(
    1. L left
    ),
  2. TR fnR(
    1. R right
    )
)

Transform values of Left and Right

Implementation

Future<Either<TL, TR>> either<TL, TR>(
        TL Function(L left) fnL, TR Function(R right) fnR) =>
    this.then((either) => either.either(fnL, fnR));