On 17/11/2007, Ian Lynagh
Hi all,
This got a warm reception when I mentioned it in http://www.haskell.org/pipermail/haskell-cafe/2007-June/027557.html so I'm formally proposing it now. It's trac #1902: http://hackage.haskell.org/trac/ghc/ticket/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 haskell-src/Language/Haskell/Lexer.hs.
Initial deadline: 1 Dec 2007.
Thanks Ian
This is a move in the opposite direction from what I'd really like to see. The Int type is usually a premature optimisation, and I usually prefer to work with Integer as much as possible, but this just means more fromIntegral conversions (or the use of the awkwardly named general version). I would much prefer for length, !!, etc. to have more general types, not less general (with compiler specialisation on Int of course). This change would be annoying. - Cale