This came up a few times already and it really isn't as wrong as it sounds. In Haskell all "side effects", which include memory stores, are in the IO monad (wit

This came up a few times already and it really isn't as wrong as it sounds. In Haskell all "side effects", which include memory stores, are in the IO monad (with a few exceptions). Writing a global variable is a side effect, because you change something other than the return value of a function. Reading would still break functional extensionality: Calling a function with equal arguments might yield different results in different contexts.