Decode the given hcursor.
Combine two decoders.
Decode the given Json value.
Monadically bind a function over this Decoder.
Convert to a Kleisli arrow.
Map a function over this Decoder.
Run two decoders.
Run one or another decoder.
Decode the given acursor.
Build a new instance that fails if the condition does not hold.
Build a new instance with the specified error message.
Choose the first succeeding decoder.