bug in instance Read Int

Simon Marlow simonmar at microsoft.com
Tue Jun 1 05:12:20 EDT 2004


On 31 May 2004 11:24, Malcolm Wallace wrote:

> The Haskell'98 Report specifies that 'read'ing an Int should accept
> only decimal notation
> 
>     instance Read Int where
>         readsPrec p = readSigned readDec
> 
> (or near equivalent), yet ghc seems to read hexadecimal Ints.
> 
>     Prelude> show (Char.chr (read "0x2B" :: Int))
>     "'+'"
>     Prelude>
> 
> Ghc's behaviour seems entirely reasonable, but it does not conform
> to the Report.  Should we regard this as a bug in the definition
> therefore?  Is there an on-going errata list for the final Revised
> Report?

I think we class this as a "deliberate deviation" from Haskell 98 in
GHC.  It's even documented; see:

http://www.haskell.org/ghc/docs/latest/html/users_guide/bugs-and-infelic
ities.html#VS-HASKELL-DEFN

Cheers,
	Simon




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