explicit signatures and default for integer literals

Mirko Rahn rahn at ira.uka.de
Tue May 31 04:24:17 EDT 2005

>>>Answer: Since somewhere an instance e.g. New [(a,Double)] (Map a Int)
>>>could be defined, leading to problems when threating 0 as (0::Int).

> There could be such an instance, but that's obviously not the case. 

No, suppose module A is the module with the definitions as before.


module B where

import A

instance New [(a,Double)] (Map a Int) where ...

When compiling A ghc cannot be sure, that there is no such instance, 
since it could be defined elsewhere.


-- Mirko Rahn -- Tel +49-721 608 7504 --
--- http://liinwww.ira.uka.de/~rahn/ ---

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