From leledumbo_cool at yahoo.co.id  Wed May 14 07:30:37 2008
From: leledumbo_cool at yahoo.co.id (leledumbo)
Date: Wed May 14 07:24:22 2008
Subject: [Hugs] Hugs doesn't know List Difference operator (\\)
Message-ID: <17228971.post@talk.nabble.com>


I'm reading some Haskell Tutorial when I arrive at List Difference operator,
which is \\. But when I try on Hugs, it responded: ERROR - Undefined
variable "\\"
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From haskell at pkturner.org  Wed May 14 07:44:16 2008
From: haskell at pkturner.org (Scott Turner)
Date: Wed May 14 07:37:59 2008
Subject: [Hugs] Hugs doesn't know List Difference operator (\\)
In-Reply-To: <17228971.post@talk.nabble.com>
References: <17228971.post@talk.nabble.com>
Message-ID: <200805140744.16375.haskell@pkturner.org>

On 2008 May 14 Wednesday, leledumbo wrote:
> I'm reading some Haskell Tutorial when I arrive at List Difference
> operator, which is \\. But when I try on Hugs, it responded: ERROR -
> Undefined variable "\\"

Add 'import List' to your program.

Or if you're running the Hugs interpreter with no program, do
     Hugs> :l List

From leledumbo_cool at yahoo.co.id  Fri May 16 03:24:17 2008
From: leledumbo_cool at yahoo.co.id (leledumbo)
Date: Fri May 16 03:17:56 2008
Subject: [Hugs] elem of infinite set of tuple
Message-ID: <17268995.post@talk.nabble.com>


I don't know how Haskell should behave on this. Consider this function:
elemOf (x,y) = (x,y) `elem` [ (a,b) | a <- [0..], b <- [0..] ]

If I try to query elemOf (1,1), the interpreter keeps searching and
searching but it never makes it. But if I query elemOf (0,1) (or anything as
long as the first element is 0), it can find it easily. I wonder how Hugs
handles this.

>From my point of view, instead of starting from (1,0), Hugs starts from
(0,0), which will never finish since the limit of the second element is
infinite.
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From ndmitchell at gmail.com  Fri May 16 05:46:26 2008
From: ndmitchell at gmail.com (Neil Mitchell)
Date: Fri May 16 05:40:04 2008
Subject: [Hugs] elem of infinite set of tuple
In-Reply-To: <17268995.post@talk.nabble.com>
References: <17268995.post@talk.nabble.com>
Message-ID: <404396ef0805160246ld41ef8i66d9f78111e4e753@mail.gmail.com>

Hi

This is not the right emailing list for this - its not a bug in Hugs,
just the way Haskell works. I recommend you resend this email to
haskell-cafe -AT- haskell.org - that is a more general list and people
will be happy to help, plus you'll reach a much bigger audience.

Alternatively, hop on to IRC: http://www.haskell.org/haskellwiki/IRC_channel

There people will be happy to answer your questions in real time :)

Thanks

Neil

>  I don't know how Haskell should behave on this. Consider this function:
>  elemOf (x,y) = (x,y) `elem` [ (a,b) | a <- [0..], b <- [0..] ]
>
>  If I try to query elemOf (1,1), the interpreter keeps searching and
>  searching but it never makes it. But if I query elemOf (0,1) (or anything as
>  long as the first element is 0), it can find it easily. I wonder how Hugs
>  handles this.
>
>  >From my point of view, instead of starting from (1,0), Hugs starts from
>  (0,0), which will never finish since the limit of the second element is
>  infinite.
>
> --
>  View this message in context: http://www.nabble.com/elem-of-infinite-set-of-tuple-tp17268995p17268995.html
>  Sent from the Haskell - Hugs-Bugs mailing list archive at Nabble.com.
>
>  _______________________________________________
>  Hugs-Bugs mailing list
>  Hugs-Bugs@haskell.org
>  http://www.haskell.org/mailman/listinfo/hugs-bugs
>