Hi.
I want to use GHCi as the interface to my Application. The simple
solution is to have the Application store its state in global IORefs.
A user can then start up ghci with -package Application and use the
provided functions to communicate with the Application. This works
nicely.
Now the tricky part. I want the user to be able to implement her own
layers on top of the Application API. A typical user interaction
could look something like this:
$ ghci -package Application
*Application:API> startApplication
*Application:API> :load UserLayer
*main:UserLayer> myCleverFunction 42
The problem, of course, is that as soon as the user says ':load' ghci
forgets all about the state of the Application. My solution to the
problem is to compile my own version of ghci (copy InteractiveUI.hs
and use -package ghc) and remove the call to rts_revertCAFs when
loading new modules. This seems to work, but since I don't really
have a clue what I'm doing I wanted to ask a few questions:
1) What is a CAF?
2) What breaks down if you don't revert them?
3) Does not reverting the CAFs really solve my problem?
/ Ulf
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