even offer pre-built definitions in their core libraries for the general monad structure and common instances.

Overview

"For a monad m, a value of type m a represents having access to a value of type a within the context of the monad." --C. A. McCann

More exactly, a monad can be used where unrestricted access to a value is inappropriate for reasons specific to the scenario. In the case of the Maybe monad, it is because the value

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