No principled reason. I wish there was no limit, which would involve generating code on the fly for instances that weren't pre-generated, but I never got around to implementing that. So you have to stop somewhere. Actually the Report says it should have Show instances up to 15 at least, but GHC doesn't. That isn't deliberate, and I guess we should fix it. Simon | -----Original Message----- | From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Stijn | De Saeger | Sent: 06 March 2005 09:40 | To: haskell-cafe@haskell.org | Subject: [Haskell-cafe] tuples and Show in GHC | | 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. | _______________________________________________ | Haskell-Cafe mailing list | Haskell-Cafe@haskell.org | http://www.haskell.org/mailman/listinfo/haskell-cafe