October 2006 - Hugs-Users

Record puns, time for removal?
by Neil Mitchell 30 Oct '06

30 Oct '06

Hi, I was just looking into Yhc and noticed that it supports record puns, for example the following code: ------ module Main where data Point = Point {x :: Int, y :: Int} main = print $ f $ Point 1 2 f (Point{x}) = x ------ Works fine in Yhc and Hugs, but not in GHC. Is this feature supported/encouraged or is it depreciated and scheduled for removal? I am tempted to remove this feature from Yhc since it seems no one uses it, and GHC doesn't know about it, but was wondering what the Hugs plans were for it first. Thanks Neil

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Re: [Hugs-users] Record puns, time for removal?
by Richard A. O'Keefe 30 Oct '06

30 Oct '06

What is a "record PUN"? Looking at the example, > module Main where > data Point = Point {x :: Int, y :: Int} > main = print $ f $ Point 1 2 > f (Point{x}) = x is the problem that "x" is used simultaneously as a field selector and a variable? Something very similar is accepted by SML/NJ: datatype point = POINT of { x : int, y : int }; fun f (POINT {x, y}) = x; print (Int.toString (f (POINT {x = 1, y = 2})) ^ "\n"); The MLton compiler also likes it. I should also point out that it's not just Yhc and Hugs that like the Haskell version; the copy of hbc I have also likes it.

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converting to capital letters
by Alex Teslin 19 Oct '06

19 Oct '06

Hi, I am a newbie in Haskell and have some problem of defining a function that would convert all small letters to capital and leave the rest intact. I have managed to do with two functions: capitalise :: String -> String capitalise xs = [capitalise2 ch| ch<-xs] capitalise2 :: Char -> Char capitalise2 ch | isLower ch = chr (ord ch - 32) | otherwise = ch But in the book exercise it asks to define as a single function. I tried like this: capitalise :: String -> String capitalise xs = [chr (ord ch - 32) | ch<-xs, isLower ch] But this returns only converted characters, the rest is ignored. Any help would be much appriciated. Send instant messages to your online friends http://uk.messenger.yahoo.com

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