[Haskell-cafe] List manipulation

[Luca Marchetti]

Hi

why don't you try something like this:

map (\(x,y) -> x+y) (zip [1,2,100] [2,3,500])

list comprehension would sum every element of the firs list with every
element of the second.

On Wed, 2005-01-26 at 17:39 +0100, Dmitri Pissarenko wrote:
> Hello!
> 
> I have two lists of Double with equal length and want to create a third one,
> in which each element is the sum of the corresponding element of the first
> list and the second list.
> 
> If list1 is [1, 2, 100] and list2 is [2, 3, 500], then the result of the
> operation I desire is [3, 5, 600].
> 
> I wrote this function
> 
> <function>
> add2Img :: [Double] -> [Double] -> [Double]
> add2Img summand1 summand2 = sum
> 	where sum = [ (x+y) | x <- summand1, y <- summand2 ]
> </function>,
> 
> but I'm getting
> 
> [3.0,4.0,501.0,4.0,5.0,502.0,102.0,103.0,600.0]
> 
> instead of
> 
> [1, 2, 100].
> 
> What is wrong with the function above?
> 
> TIA
> 
> Dmitri Pissarenko
> --
> Dmitri Pissarenko
> Software Engineer
> http://dapissarenko.com
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-- 

  Luca Marchetti
  Senior Application Specialist

  Bizmatica S.p.A.
  Via Pietrasanta, 14 - Building 3a
  20141 Milano, Italy

  e-mail:  luca.marchetti at bizmatica.com