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  • Glasgow Haskell Compiler
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  • #12804
Closed
Open
Created Nov 04, 2016 by tomjaguarpaw@trac-tomjaguarpaw

forever contains a space leak

  1. 9.0.0's forever (implemented in terms of Applicative) has a space leak for certain base Monads. The old forever (implemented in terms of Monad) does not.

See these messages for details

  • https://mail.haskell.org/pipermail/haskell-cafe/2016-October/125177.html
  • https://mail.haskell.org/pipermail/haskell-cafe/2016-October/125178.html
  • https://mail.haskell.org/pipermail/haskell-cafe/2016-November/125443.html

This is not necessarily forever's fault. It seems likely that the broken behaviour that occurs with ReaderT and StateT (on IO) could be fixed by a specialised implementation of *> (for ReaderT and StateT).

Perhaps, then, this bug should ultimately be fixed in transformers (and various other packages which supply Applicatives) but it is a regression introduced by base-4.9.0.0 so I think it's worthwhile to discuss here.

Trac metadata
Trac field Value
Version 8.0.1
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component libraries/base
Test case
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