[Haskell-cafe] tuples and Show in GHC
Stijn De Saeger
stijndesaeger at gmail.com
Sun Mar 6 04:40:09 EST 2005
hi all,
Is there a principled reason why in GHC tuples with up to five
elements automatically derive from the Show class but from six
elements and up they don't anymore? If this is not a bug I would be
very curious to hear what the reasoning behind this is....
below is an example of said behaviour :
> type MyInt1 = (Int,Int,Int,Int,Int)
> myInt1 :: MyInt1
> myInt1 = (1,2,3,4,5)
> type MyInt2 = (Int,Int,Int,Int,Int,Int)
> myInt2 :: MyInt2
> myInt2 = (1,2,3,4,5,6)
....
*HS> myInt1
Loading package haskell98 ... linking ... done.
(1,2,3,4,5)
*HS> myInt2
<interactive>:1:
No instance for (Show MyInt2)
arising from use of `print' at <interactive>:1
In a 'do' expression: print it
*HS>
stijn.
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