[Haskell-cafe] STM and FFI

[Jules Bean]

Ryan Ingram wrote:
> If the function isn't pure, you need to do a lot more proofs to assure
> that this is safe.  In particular, the function must be able to be
> called with invalid input.  If you are confident that this is the
> case, you can use unsafeIOToSTM to convert a call to that function
> into an STM primitive.

...not only must it be safe to be called with invalid inputs, but it 
most not have any long-term effects, whether the input is valid or 
invalid, since I do not believe that there is any way for the function 
to 'undo' its effect at 'retry' time.

Jules