context-stack GHC 7.0.1 Release Candidate 1

Simon Peyton-Jones simonpj at
Mon Oct 25 05:07:10 EDT 2010

Implementing fundeps in the new solver has proved more complicated than we thought at first.  I’m not aware of any obvious “oh, this is going to perform really badly” parts.  My gut feel is that the inference engine will work better using type functions, but I can’t put any real evidence behind that claim.  If you have a low-cost way to experiment we’d love to hear what you find.  But don’t burn a month converting in case it makes no difference!


From: glasgow-haskell-users-bounces at [mailto:glasgow-haskell-users-bounces at] On Behalf Of Corey O'Connor
Sent: 22 October 2010 19:50
To: Simon Peyton-Jones
Cc: glasgow-haskell-users at
Subject: Re: context-stack GHC 7.0.1 Release Candidate 1

I was running into a similar issue and haven't noticed a dramatic improvement with the latest changes. The number of ticks taken to compile are approximately the same before and after the latest patch. However the system still compiles just fine with a context stack of 200. Which is OK by me.

The system I'm working with uses functional dependencies and type families w/ type equalities. Could I improve the performance of my system by replacing the functional dependencies with type families & type equalities?

The part of the system that uses functional dependencies is monad-param:

The other part of the system I can't release the source to yet. :-\ I know, not very useful.

-Corey O'Connor
coreyoconnor at<mailto:coreyoconnor at>

On Tue, Oct 19, 2010 at 8:57 AM, Simon Peyton-Jones <simonpj at<mailto:simonpj at>> wrote:

Dimitrios and I (mainly D) have fixed this.  Your system compiles nicely now. Can you try again with the HEAD?


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