[Haskell-cafe] Propositional logic implementation

[Ryan Ingram]

I like using smart constructors to replace :<=>: and :=>:

a \/ b = a :\/: b
a /\ b = a :/\: b
a ==> b = Not a \/ b
a <=> b = (a ==> b) /\ (b ==> a)

Also, if you generalize Sentence a bit you get a really nice
formulation of "true".  See my paste at http://hpaste.org/13807#a2

  -- ryan

2009/1/10 Andrew Wagner <wagner.andrew at gmail.com>:
> Nice Idea, though I don't know that I want something that extensive. I was
> more looking for whether there was a better way I could define the algebraic
> data type.
>
> On Sat, Jan 10, 2009 at 6:04 PM, Miguel Mitrofanov <miguelimo38 at yandex.ru>
> wrote:
>>
>> Look at SYB (Data.Data, Data.Generics.*). For example, your "symbols"
>> function can be rewritten as
>>
>> symbols :: Sentence -> [Symbol]
>> symbols s = nub $ listify (const True) s
>>
>> "true" is not that simple, because this code is NOT boilerplate - each
>> alternative is valuable by itself.
>>
>> On 10 Jan 2009, at 23:56, Andrew Wagner wrote:
>>
>>> All,
>>> Is there some better way to do this? It seems like a lot of boilerplate.
>>> Thanks!
>>>
>>> http://hpaste.org/13807#a1
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>
>
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