#13457: unsafeInterleaveST is too unsafe -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Core Libraries | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by ekmett): If you don't read or write to the same STRef (or STArray element) like you state (and don't use unsafeIOToST, etc.) then this is a sufficient condition for your operation to be idempotent. =) You can actually strengthen to not reading from a ref that you write to before you write to it. The write washes away your sins by destroying any information leaked. I actually exploit that extra structure in my monadic revisions code. But again, this is just a weak way to state a demand for idempotence. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13457#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler