getValueEither
Returns the value of mapkey as Either.Right, if it exists, or as Either.Left otherwise.
Receiver
the map on which the key is requested
Return
Either of the request
Parameters
key
requested key to be accessed
Returns the value of listindex as Either.Right, if it exists, or as Either.Left otherwise.
Receiver
the map on which the index is requested
Return
Either of the request
Parameters
index
requested key to be accessed