The issue with this example is that you have genericTake :: Integral a => a -> [b] -> [b] where the 'a' is converted to an Int without being checked for overflow. IMHO type defaulting is irrelevant for this one problem; evaluating
take 444444444444444444444444444444 "foobar"
has exactly the same result without any defaulting taking place. Arguably fromIntegral could have other behavior (error/exception/Maybe) when a conversion would overflow, but that seems like a very significant change. Aside from this example, I'm quite sympathetic to the issue. I've more than once defined values as let two = 2 :: Int three = 3 :: Int solely to suppress warnings about type defaulting for (^n). Really, I'd prefer to see the Prelude export (^) :: Num a => a -> Int -> a I think that's the most common case, and it's probably never useful to raise to a power greater than (maxBound :: Int). John L. On Thu, Apr 11, 2013 at 8:10 AM, Tom Ellis < tom-lists-haskell-cafe-2013@jaguarpaw.co.uk> wrote:
On Thu, Apr 11, 2013 at 12:56:05AM +0100, Barak A. Pearlmutter wrote:
... in most of the cases I do want this warnings. It's possible to get something default to Integer when it should be Int. There are only few cases when it's not appropriate. Only ^ and ^^ with literals I think
There are a few other cases, albeit less annoying. Like this:
c = fromIntegral 2 :: Int
Granted this is silly code, but the same case arises inside pretty much any code that is generic over Integral, in which case the warning you get is not the *right* warning. Example:
genericTake n xs = take (fromIntegral n) xs genericTake 444444444444444444444444444444 "foobar"
Hi Barak,
I don't write a lot of numeric code so I am under-educated in this area. Could you write a more substantial example so I get a clearer idea of what's going on?
Thanks,
Tom
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