PROPOSAL: Restrict the type of (^), (^^), and add genericPower,
lennart at augustsson.net
Sun Nov 18 13:44:22 EST 2007
I think this proposal goes the wrong way. We should not make types more
specific, but more general.
Instead of ruining ^ and ^^, lets make the type of length, take, etc more
On Nov 17, 2007 2:02 PM, Ian Lynagh <igloo at earth.li> wrote:
> Hi all,
> This got a warm reception when I mentioned it in
> so I'm formally proposing it now. It's trac #1902:
> Note that this is a divergence from Haskell 98 (but the libraries
> already have a handful of small divergences, and Haskell' is just around
> the corner...).
> In my opinion, (^) has the wrong type. Just as we have, for example,
> (!!) :: [a] -> Int -> a
> genericIndex :: (Integral b) => [a] -> b -> a
> we should also have
> (^) :: (Num a) => a -> Int -> a
> genericPower :: (Num a, Integral b) => a -> b -> a
> (or some other function name). The same goes for (^^) (genericPower').
> In my experience this would remove 99.9% of all defaulting (mostly where
> you write things like x^12 and 8^12), which means it's easier to get
> -Wall clean without having to put :: Int annotations everywhere.
> The impact to GHC's bootlibs and extralibs is minimal. In most cases we
> have things like 2^15, where Int is clearly fine, although it happens to
> be defaulted to Integer currently. In Data.Complex we have 2 cases of
> e^(2::Int) which can now be beautified. There are several cases where
> the type is inferred to be Int anyway.
> There are 3 files where we really do have an Integer, and it does
> matter. They are all for parsing numbers of the form 18e43, in
> base/Text/Read/Lex.hs, parsec/Text/ParserCombinators/Parsec/Token.hs and
> Initial deadline: 1 Dec 2007.
> Libraries mailing list
> Libraries at haskell.org
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