úέNoneA mutable variable in the  monad.  Build a new . Write a new value into a . Write a new value into a . Mutate the contents of a . Be warned that - does not apply the function strictly. This  means if the program calls # many times, but seldomly uses the A value, thunks will pile up in memory resulting in a space leak. Strict version of    fay-ref-0.1.0.0FayRef newFayRef readFayRef writeFayRef modifyFayRef modifyFayRef' fay-0.14.1.0 Fay.TypesFay