Really bad code for single method dictionaries?

[Simon Peyton-Jones]

I would like to know more too. No one told me!

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-haskell-users-
| bounces at haskell.org] On Behalf Of Jason Dusek
| Sent: 26 March 2009 23:30
| To: glasgow-haskell-users at haskell.org
| Subject: Really bad code for single method dictionaries?
|
|   I was reading the stream fusion code today and came across a comment stating
|   that single element dictionaries interacted poorly with GHC's optimizer:
|
|     class Unlifted a where
|
|       [...]
|       expose [...]
|
|       -- | This makes GHC's optimiser happier; it sometimes produces really bad
|       -- code for single-method dictionaries
|       --
|       unlifted_dummy [...]
|
|   A cursory search on GHC's Trac shows no corresponding bug; is this no longer
|   a problem? A small problem? I would like to know more about it.
|
| --
| Jason Dusek
|
|
|
|  |...stream fusion code...|
|   http://www.cse.unsw.edu.au/~dons/code/streams/list/Data/Stream.hs
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