If fa has an a, return it; otherwise it must be universally
quantified.
Returns some if this context is defined, otherwise none.
Returns the value within the context if defined or else the value of default.
Returns true if a value is defined within the context.
Returns true if no value is defined within the context.
Returns true if a value is defined within the context.
Returns true if a value is defined within the context. This is an alias for isDefined.
Returns given context if it is defined or else the value of the alternative.
Returns this context converted to the Maybe context.
Returns this context converted to the Option context.
Abstraction over a container/context which may or may not provide a value.
the container/context type
syntax.OptionalOps