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Today's Topics:
1. Re: Data structure for Propositional Logic formulas
(Daniel Schoepe)
2. Re: first open source haskell project and a mystery to boot
(Lorenzo Bolla)
3. Re: Data structure for Propositional Logic formulas
(Christian Maeder)
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Message: 1
Date: Wed, 12 Oct 2011 23:33:51 +0200
From: Daniel Schoepe <dan...@schoepe.org>
Subject: Re: [Haskell-beginners] Data structure for Propositional
Logic formulas
To: Alexander Raasch <i...@alexraasch.de>, beginners@haskell.org
Message-ID: <874nzddhds.fsf@gilead.invalid>
Content-Type: text/plain; charset="us-ascii"
On Wed, 12 Oct 2011 22:58:47 +0200, Daniel Schoepe <dan...@schoepe.org> wrote:
> data Formula = Literal | And .......
Sorry, that should have been:
data Formula = Lit Literal | ...
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Message: 2
Date: Thu, 13 Oct 2011 09:47:35 +0100
From: Lorenzo Bolla <lbo...@gmail.com>
Subject: Re: [Haskell-beginners] first open source haskell project and
a mystery to boot
To: Alia <alia_kho...@yahoo.com>
Cc: "beginners@haskell.org" <beginners@haskell.org>
Message-ID:
<CADjgTRxo=ut-tl_aqdidsbr8hak+a_dawmz8dp9ay+rk_j5...@mail.gmail.com>
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Hi,
On Wed, Oct 12, 2011 at 7:59 PM, Alia <alia_kho...@yahoo.com> wrote:
>
> I would appreciate if anyone could shed some light on this whimsical
> problem.
>
> In case you are wondering why this is relevant to the beginner's forum.
> Well...
>
> firstly, I am a beginner, and, er... the code is short enough to serve
> pedagogical purposes (-;
>
>
I'm a beginner, too, so my suggestions are not at all authoritative...
> --t5 = id3 [a1,a2,a3,a4] [d1,d2,d3,d4]
>
Can you not use any of the techniques described here:
http://haskell.org/haskellwiki/Heterogenous_collections?
For example, using a tuple or dynamic types.
my 2 cents,
L.
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Message: 3
Date: Thu, 13 Oct 2011 11:12:10 +0200
From: Christian Maeder <christian.mae...@dfki.de>
Subject: Re: [Haskell-beginners] Data structure for Propositional
Logic formulas
To: Benedict Eastaugh <ionf...@gmail.com>
Cc: beginners@haskell.org
Message-ID: <4e96ab6a.2020...@dfki.de>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Am 12.10.2011 23:24, schrieb Benedict Eastaugh:
> Hi Alex,
>
> since Daniel has done a nice job of actually answering your questions,
> I shall just note that I have a module similar to this available on
> Hackage as part of my hatt package, which generates truth tables for
> formulae in classical propositional logic.
>
> http://hackage.haskell.org/package/hatt
> http://hackage.haskell.org/packages/archive/hatt/1.3.0/doc/html/Data-Logic-Propositional.html
Why do most people like duplicate or repeated code?
Instead of
data Expr = Variable String
| Negation Expr
| Conjunction Expr Expr
| Disjunction Expr Expr
| Conditional Expr Expr
| Biconditional Expr Expr
you are usually better served by:
data Expr = Variable String
| Negation Expr
| Junct BinOp Expr Expr
data BinOp = Conjunction | Disjunction | Conditional | Biconditional
Cheers Christian
>
> Benedict
>
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