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Today's Topics:
1. appropriateness of haskell for GUIs (Michael P Mossey)
2. Re: Fractional Int (Brandon S. Allbery KF8NH)
3. Re: Fractional Int (Zachary Turner)
4. Re: Fractional Int (Brandon S. Allbery KF8NH)
5. Re: Fractional Int (Brandon S. Allbery KF8NH)
6. Re: appropriateness of haskell for GUIs (Andy Elvey)
----------------------------------------------------------------------
Message: 1
Date: Fri, 20 Mar 2009 16:16:38 -0700
From: Michael P Mossey <[email protected]>
Subject: [Haskell-beginners] appropriateness of haskell for GUIs
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hello, I'm totally new to Haskell. I'm thinking of using it for a
personal project, which is a gui-based musical score editor. (*) Why
Haskell? I've always been interested in proving my software's
correctness, usually in practical and informal sense. In other words, I
would like to reduce bugs by having a really good understanding of what
my software does. I also just want to learn Haskell.
Before I invest a lot of time in learning Haskell, however, I want to
understand if it's the right language for doing a gui-based musical
score editor. First of all, I need a gui toolkit of some sort, and I
notice that bindings to Qt exist. I'm already very familiar with Qt, so
that's good. I also need to access the Windows midi api, and I see there
is a module called hmidi.
However, a gui program is essentially event driven and heavily interacts
with the outside world. I don't know how compatible these ideas are with
Haskell.
If I don't use Haskell, I will probably use Python, which I already know
well. So basically the question is: Haskell or Python? Note: I would
enjoy learning Haskell, so this is not a question of which language is
better in an absolute sense... if Haskell is suitable, but not the best
choice, I will still probably use it.
Thanks,
Mike
(*) For those who ask why I'm doing my own music score editor when many
already exist, it's because it needs to be integrated with my own
computer-assisted composition system. As an editor, it will be
primitive: that's not its main purpose.
------------------------------
Message: 2
Date: Fri, 20 Mar 2009 19:37:32 -0400
From: "Brandon S. Allbery KF8NH" <[email protected]>
Subject: Re: [Haskell-beginners] Fractional Int
To: Sean Bartell <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
On 2009 Mar 20, at 18:01, Sean Bartell wrote:
> For a type "a" to be Fractional requires there to be:
> (/) :: a -> a -> a
> You can't divide an Int by another Int and (in general) get a third
> Int. You would probably want something like a "Fractionable"
> typeclass, with
> (/) :: a -> a -> b
> which would result in a Rational, but Haskell doesn't have this.
...but there is (%) :: (Integral a) => a -> a -> Ratio a
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [email protected]
system administrator [openafs,heimdal,too many hats] [email protected]
electrical and computer engineering, carnegie mellon university KF8NH
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Message: 3
Date: Fri, 20 Mar 2009 19:07:45 -0500
From: Zachary Turner <[email protected]>
Subject: Re: [Haskell-beginners] Fractional Int
To: [email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
2009/3/20 Brandon S. Allbery KF8NH <[email protected]>
> On 2009 Mar 20, at 18:01, Sean Bartell wrote:
>
>> For a type "a" to be Fractional requires there to be:
>> (/) :: a -> a -> a
>> You can't divide an Int by another Int and (in general) get a third
>> Int. You would probably want something like a "Fractionable"
>> typeclass, with
>> (/) :: a -> a -> b
>> which would result in a Rational, but Haskell doesn't have this.
>>
>
>
> ...but there is (%) :: (Integral a) => a -> a -> Ratio a
>
Thanks, I knew about % but didn't remember about it when I was working on
this sample :) So that being said, consider the following:
Prelude Data.Ratio> let x = 5::Int
Prelude Data.Ratio> :t x
x :: Int
Prelude Data.Ratio> :t (x%3)
(x%3) :: Ratio Int
Prelude Data.Ratio> let y = truncate (x%3)
Prelude Data.Ratio> :t y
y :: Integer
Why does y now have the type Integer instead of Int?
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Message: 4
Date: Fri, 20 Mar 2009 20:14:38 -0400
From: "Brandon S. Allbery KF8NH" <[email protected]>
Subject: Re: [Haskell-beginners] Fractional Int
To: Zachary Turner <[email protected]>
Cc: [email protected]
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Message: 5
Date: Fri, 20 Mar 2009 20:18:41 -0400
From: "Brandon S. Allbery KF8NH" <[email protected]>
Subject: Re: [Haskell-beginners] Fractional Int
To: Zachary Turner <[email protected]>
Cc: beginners beginners <[email protected]>
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Message: 6
Date: Sat, 21 Mar 2009 19:58:03 +1300
From: Andy Elvey <[email protected]>
Subject: Re: [Haskell-beginners] appropriateness of haskell for GUIs
To: Michael P Mossey <[email protected]>
Cc: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Michael P Mossey wrote:
> Hello, I'm totally new to Haskell. I'm thinking of using it for a
> personal project, which is a gui-based musical score editor. (*) Why
> Haskell? I've always been interested in proving my software's
> correctness, usually in practical and informal sense. In other words,
> I would like to reduce bugs by having a really good understanding of
> what my software does. I also just want to learn Haskell.
>
> Before I invest a lot of time in learning Haskell, however, I want to
> understand if it's the right language for doing a gui-based musical
> score editor. First of all, I need a gui toolkit of some sort, and I
> notice that bindings to Qt exist. I'm already very familiar with Qt,
> so that's good. I also need to access the Windows midi api, and I see
> there is a module called hmidi.
>
> However, a gui program is essentially event driven and heavily
> interacts with the outside world. I don't know how compatible these
> ideas are with Haskell.
>
> If I don't use Haskell, I will probably use Python, which I already
> know well. So basically the question is: Haskell or Python? Note: I
> would enjoy learning Haskell, so this is not a question of which
> language is better in an absolute sense... if Haskell is suitable, but
> not the best choice, I will still probably use it.
>
> Thanks,
> Mike
>
> (*) For those who ask why I'm doing my own music score editor when
> many already exist, it's because it needs to be integrated with my own
> computer-assisted composition system. As an editor, it will be
> primitive: that's not its main purpose.
> _______________________________________________
Hi Michael -
I'm also new to Haskell. Although I can't really give a definitive
answer as to whether Haskell is appropriate for GUIs, I can mention
several GUI libraries that exist for Haskell. They are wxHaskell,
Gtk2Hs and qtHaskell.
The following page mentions those and a number of others -
http://www.haskell.org/haskellwiki/Applications_and_libraries/GUI_libraries
Note - that page says that "there is no standard (GUI lib) and all are
more or less incomplete." Don't be too put off by that - from what I've
seen, although I haven't used them myself, both wxHaskell and Gtk2HS now
seem to be quite complete. I can't really comment on qtHaskell as I
haven't seen that in action.
- Hope this helps....
- Andy
------------------------------
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