Ryan Ingram wrote:
Congratulations, you're halfway to reinventing ST! :)
Except that, AFAIK, ST doesn't provide the "hey you can store anything and retrieve it later" trick. ;-) I did however wonder if there wasn't some way I could use an extra phantom type to somehow "tag" which thread a key was generated in... but I couldn't figure out how to make it work.
Here's the "trick" [1]:
data Storage s x ... data Key s v ...
Now add the extra "s" parameter to all the functions that use Storage & Key.
run :: (forall s. Storage s x) -> x
Now you can't save keys between sessions; the type "s" isn't allowed to escape the "forall" on the left of the function arrow!
Ah, I see. It sounds so easy when you already know how... :-) BTW, does anybody know how rank-N types are different from existential types?