Re: Automatic derivation

[haskell-request@cs.glasgow.ac.uk]

Date: 22 Apr 91  9:33
From: haskell-request@cs.glasgow.ac.uk
Sender: Philip Wadler <wadler@cs.glasgow.ac.uk>
To: cvh@cs.glasgow.ac.uk, haskell@cs.glasgow.ac.uk, kh@cs.glasgow.ac.uk
Subject: Re:  Automatic derivation

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| > What happens if you write
| > 
| > data T1 = C1 deriving Ix
| 
| I would say that *if* the required instances aren't explicitly provided
| by instance declarations, then this should be an error.  It's confusing
| to sometimes derive instances, sometimes not.

I agree with Kevin.  -- P