I infer from the following dialog that ghci nontransparently caches knowledge about the contents of the library. This is doubtless helpful for the flurry of imports that a single "load" or interactive "import" may cause. But the time saved by caching from one such top-level action to the next is probably imperceptible. The hours wasted in the present instance and others like it (the very quick response on cafe suggests that it's not unusual) probably outweigh all the milliseconds that the cache normally saves. Non-transparent caching is inherently evil. While the risk may be justifiable in some cases (e.g. stdio buffers in C), it is very questionable at top level in ghci. Doesn't this warrant a ticket? Doug

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I install the indexed package by using cabal

Cabal install indexed

https://hackage.haskell.org/package/indexed

Seemed to do something.

Then I want to use that package...

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import Control.Monad.Indexed

Boom...unknown...

Possibly silly question but... did you restart `ghci` after installing indexed?

Genius Maybe this Haskell lark isnt as hard as I thought....