MonadFix - HaskellWiki

The MonadFix typeclass provides the mfix method for value recursion. It can be used directly, or indirectly through the RecursiveDo extension. The GHC Users Guide has a section on RecursiveDo. It is useful for building cyclic data in monadic code. What it is not and what it is It is tempting to see “recursion” and guess it means performing actions recursively or repeatedly. No. It means recursion

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“An action may use a value to be returned by the same action, or even returned by another action several lines of code later. Some uses are: creating cyclic data structures; using monadic code to specify a graph or network.”