Orphan Instances

Simon Peyton-Jones simonpj at microsoft.com
Tue Aug 12 14:25:59 EDT 2008


Suggestions like this are a great help for improving the user manual.  Thank you.  I will fix.

Simon

| -----Original Message-----
| From: glasgow-haskell-users-bounces at haskell.org [mailto:glasgow-haskell-
| users-bounces at haskell.org] On Behalf Of Yitzchak Gale
| Sent: 12 August 2008 16:48
| To: Simon Peyton-Jones
| Cc: GHC Users Mailing List; Ashley Yakeley
| Subject: Re: Orphan Instances
|
| <Moving this side point to the ghc users list...>
|
| Ashley Yakely wrote:
| >> What is an orphan instance, and why do we care about them?
|
| Simon Peyton-Jones wrote:
| > They are documented in the GHC manual
| > http://www.haskell.org/ghc/docs/latest/html/users_guide/separate-
| compilation.html#orphan-modules
|
| Thanks for the nice explanation there. Since you brought it
| up, though, the explanation might be made even clearer with
| two small changes:
|
| 1. The term "instance head" is used throughout the explanation,
| beginning already with the second paragraph ("the head of the
| instance..."). However, that term is only defined near the very end
| '(the part after the "=>")'. For those who do not already know the
| surprise ending, this makes the explanation read rather like a
| mystery story.
|
| 2. I believe that the text "by setting a = Int" was meant to be
| "by setting a = T".
|
| Thanks,
| Yitz
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