Sorry, link [2] meant to be https://ghc.haskell.org/trac/ghc/ticket/11760 21-11-2017, Аўт а 20:43 +0300, Yuras Shumovich напісаў:
Hello,
I was evaluating a possibility that linear types can break referential transparency [1], exactly like lazy ST [2].
But on the way I realized that even strict ST may suffer from the same issue. If ST computation is interrupted by e.g. async exception, runtime will "freeze" it at the point where it was interrupted [3].
So the question: is the "freezed" computation just a normal thunk? Note that the runtime doesn't guarantee that a thunk will be evaluated only once [4]. If the "freezed" thunk captures e.g. STRef, and will be evaluated twice, its effect could become observable from outside, just like in case of lazy ST.
I tried to check the theory by stress testing RTS. Unfortunately I immediately discovered a runtime crash [5], which is probably not related to my question.
Hope someone will be able to clarify things for me.
Thanks, Yuras.
[1] https://github.com/ghc-proposals/ghc-proposals/pull/91#issuecomme nt -345553071 [2] https://ghc.haskell.org/trac/ghc/ticket/14497 [3] See section 8 there: https://www.microsoft.com/en-us/research/wp- co ntent/uploads/2016/07/asynch-exns.pdf [4] https://www.microsoft.com/en-us/research/wp-content/uploads/2005/ 09 /2005-haskell.pdf [5] https://ghc.haskell.org/trac/ghc/ticket/14497