hub.darcs.net :: ross -> transformers -> issue

#31Stricter Writer

minad

Hi,

I made the packages writer-cps-mtl and writer-transformers-mtl which implement a stricter writer monad transformer in continuation passing style as was discussed before on the Haskell mailing list etc

• http://hackage.haskell.org/package/writer-cps-mtl
• http://hackage.haskell.org/package/writer-cps-transformers

See also the current reddit discussion:

https://www.reddit.com/r/haskell/comments/50hf2s/stricter_writert_and_rwst_replacements/

and the mtl issue on github:

https://github.com/ekmett/mtl/issues/38

Daniel

• andrewthadTue Sep 6 23:45:42 UTC 2016

  I agree that this should be in transformers.

• Li-yao XiaTue Mar 27 22:29:57 UTC 2018

  This issue has been brought up again recently https://www.reddit.com/r/haskell/comments/87ijm4/the_task_abstraction/dwd9dju/

  It's really not obvious from the documentation that the runtime characteristics of the default WriterT are not what most people expect, much less where to find a better alternative.

• andrewthadMon Apr 2 19:18:55 UTC 2018

  The transformers package now provides the AccumT monad transformer. This is very nearly what writer-cps-transformers offers. However, Accum is lazy in the accumulator. One easy solution would be to provide a Control.Monad.Trans.Accum.Strict module. Ross, would you accept a PR that provided this new module as well as improvement to the documentation of WriterT explaining that AccumT should be used to get a strict accumulator?

• Ross PatersonTue Apr 3 15:17:23 UTC 2018

  So we'd have strict and lazy AccumT differing only in pattern matching, like strict and lazy StateT and WriterT? That sounds good.

• andrewthadTue Apr 3 16:46:22 UTC 2018

  Cool. I can write a patch for this. I’ll try to get this up soon.

• andrewthadSun Apr 22 17:08:48 UTC 2018

  Ross, I've written up a patch for this here: https://hub.darcs.net/andrewthad/transformers/patch/b680781658c8b7b13edb59055408797ff1ab3927. I don't know how to PR in darcshub, but let me know any feedback you have.

• Ross PatersonWed May 2 18:11:54 UTC 2018

  Looking more closely, I don't think a variant of AccumT is the monad you're looking for. writer-cps-transformers is a restricted state monad.

• madgenTue Nov 20 10:35:41 UTC 2018

  What is needed to advance this issue?

• Ross PatersonThu Nov 22 07:48:39 UTC 2018
  • status set to closed

  I have incorporated the two modules from writer-cps-transformers

• madgenThu Nov 22 23:18:45 UTC 2018

  Amazing <3. Thank you!