[Haskell-cafe] Currying function using values from array

[Bulat Ziganshin]

Hello Sukit,

Friday, August 8, 2008, 3:52:51 AM, you wrote:

it requires use of typeclasses

instance C f => C (a->f)
  curry (somef::(a->f)) (someas::[a]) =
    (somef (head someas)) (tail someas)

and so on. look into hslua sources, for example:
http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hslua


> Thanks Tom and Henning for your response. Let me put the question
> in another way by generalizing and tweaking it a little bit.

> How in Haskell that I can create a function that curries any other
> function, which receives multiple parameters, by using a the input
> from a list (same data type) or a tuple (mixed data type) such that
> it either returns another closure (if not all parameters are
> curried) or the final value of the computation (when all parameters are known)?
>  
> Ed

> On Thu, Aug 7, 2008 at 12:49 PM, Tom Nielsen <tanielsen at gmail.com> wrote:
>  Maybe you want something like
>  
>  curryWithList :: ([a]->b)->[a]->([a]->b)
>  curryWithList f lst1= \lst2 ->f (lst1++lst2)
>  
>  addThemUp = sum
>  curried = curryWithList addThemUp [1,2,3,4]
>  curried [5] =15
>  

>  On Thu, Aug 7, 2008 at 8:35 PM, Henning Thielemann
>  <lemming at henning-thielemann.de> wrote:
 >>
 >> On Thu, 7 Aug 2008, Sukit Tretriluxana wrote:
 >>
 >>> Dear Haskell experts,
 >>>
 >>> I am currently studying Groovy language. An experiment I did with its
 >>> closure is to perform closure/function "curry" using an array containing the
 >>> values for the parameter binding. See the sample below.
 >>>
 >>> int addThemUp(a,b,c,d,e) { a+b+c+d+e }
 >>> def arrayCurry(arr, cls) { arr.inject(cls) { c, v -> c.curry(v) } }
 >>> println addThemUp(1,2,3,4,5)
 >>> println arrayCurry([1,2,3,4,5], this.&addThemUp)()
 >>> println arrayCurry([1,2,3,4], this.&addThemUp)(5)
 >>>
 >>> The printouts from the above code are the same, verifying that the code
 >>> works fine. Then I come to ask myself how I can do the same in Haskell. I'm
 >>> not a Haskell expert so I couldn't figure it. I wonder if you guys could
 >>> shed some light on this.
 >>
 >> I do not know Groovy, but maybe you want something like
 >>
 >>  addThemUp :: Num a => (a,a,a,a,a) -> a
 >>  addThemUp (a,b,c,d,e) = a+b+c+d+e
 >>
 >>  -- should be better named list5Curry or so
 >>  arrayCurry :: ((a,a,a,a,a) -> a) -> [a] -> a
 >>  arrayCurry cls [a,b,c,d,e] = cls (a,b,c,d,e)
 >>
 >>  print (addThemUp(1,2,3,4,5::Int))
 >>  print (arrayCurry addThemUp [1,2,3,4,5::Int])
 >>
 >> However, it's hardly of any use, since you won't use a list if the number
 >> of elements is fixed (and small) or if the elements even must have
 >> distinct types.
>  
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>  

>   


-- 
Best regards,
 Bulat                            mailto:Bulat.Ziganshin at gmail.com