- Haskell-Cafe - Haskell.org

(no subject)
by Richard Barth 13 Sep '02

13 Sep '02

I'm just learning Haskell with Hugs98. I can't understand why the line defining "foo" is acceptable while the line defining "bar" (only difference is the unary minus) generates the error message at the end. If someone could explain this, or, better yet, tell me how I can figure this out for myself. Thanks. data Entry = Ent {date :: String, amount :: Double} foo = [Ent "baz" 1.0] bar = [Ent "baz" -1.0] Type checking...... ERROR "...test.hs":7 - Unresolved top-level overloading *** Binding : bar *** Outstanding context : Fractional (Double -> Entry)

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Re: (no subject)
by Ashley Yakeley 13 Sep '02

13 Sep '02

At 2002-09-13 12:12, Richard Barth wrote: >I'm just learning Haskell with Hugs98. I can't understand why the line >defining "foo" is acceptable while the line defining "bar" (only >difference is the unary minus) generates the error message at the end. >If someone could explain this, or, better yet, tell me how I can figure >this out for myself. Thanks. > >data Entry = Ent {date :: String, amount :: Double} >foo = [Ent "baz" 1.0] >bar = [Ent "baz" -1.0] Haskell thinks it's a binary minus. Try this: bar = [Ent "baz" (-1.0)] -- Ashley Yakeley, Seattle WA

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maxList
by Nuno Silva 13 Sep '02

13 Sep '02

hello, I'm new to haskell, I'm studying for an exam, and I'm having trouble with this exercise. I have a list of Integers, and I want to return the highest value of all. i have this: comp :: Int -> Int -> Int comp x y | x < y = y | otherwise = x maxList :: [Int] -> [Int] maxList (x1:x2:xs) = comp x1 x2 : maxList xs maxList [] = [] this code returns a list, but I only want it to return a single Int... but can't seem to do it, could you please help me? --------------------------------- Do you Yahoo!? Yahoo! News - Today's headlines

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Make $20,000 with PayPal! Fast, reliable,FREE!!!
by Your Friend 13 Sep '02

13 Sep '02

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Bilgi Payla�t�k�a Artar
by info 10 Sep '02

10 Sep '02

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mutable records
by Scott J. 10 Sep '02

10 Sep '02

Hi, Is it possible to define oject types in Haskell and what does one propose to do it? Is it possible to define parts of a record with the help of the ST s monad mutable during the whole program? (As is possible in Ocamel)? Thx Scott

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RE: A problem with haskell-mode
by Simon Marlow 09 Sep '02

09 Sep '02

> I had the same problem, and I found a fix somewhere. > Don't reember what exactly I had to change so I'll just send > you my Haskell section of xemacs init.el. > > By the way I get an error whenever I type "undefined". Anyone > else noticed it? > (1) (error/warning) Error in `post-command-hook' (setting > hook to nil): > (wrong-type-argument listp a ) I'm officially the maintainer of the emacs Haskell mode since Reuben Thomas left, but I deleted the section of my brain that contained my knowledge of emacs lisp in order to make more room for GHC, so I'm not a very effective maintainer I'm afraid :( Offers to take over the maintainership are entirely welcome, but in the meantime I'm happy to add any fixes for these kinds of problems to the web page and/or the source. Cheers, Simon

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A problem with haskell-mode
by Deling Ren 06 Sep '02

06 Sep '02

Hi, all, I installed the latest version of Haskell mode for emacs. Whenever I load haskell major mode by opening a haskell file, Xemacs gives me the following error message: (1) (error/warning) Error in `post-command-hook' (setting hook to nil): (void-variable imenu--index-alist) My Xemacs version is 21.4.8. It works well under GNU emacs though. Anybody has an idea how to get around it? Thanks. Deling

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aide SVP
by fouad ktiri 30 Aug '02

30 Aug '02

Bonjour, Comment faire pour stocker des données dans une liste comme en programmation normale (x=x+1) Merci beaucoup ______________________________________________________ Boîte aux lettres - Caramail - http://www.caramail.com

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help
by yan zhong 30 Aug '02

30 Aug '02

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