# [Haskell-cafe] multMM :: Matrix -> Matrix -> Matrix --multiplies two matrices question (Homework)

Keith Sheppard keithshep at gmail.com
Fri Feb 5 09:01:28 EST 2010

```I did a blog post on basic matrix ops which may be useful to you

http://blog.keithsheppard.name/2009/06/bird-tracks-through-math-land-basic.html

It uses a 2D list representation for matrices which you would not do
for any performance critical work.

best
keith

On Wed, Feb 3, 2010 at 1:38 AM, 조광래 <kwangraecho at gmail.com> wrote:
> hi i was trying to solve it but
>
> All i got is
> type Matrix=[[Double]]
>
> multMM :: Matrix -> Matrix -> Matrix --multiplies two matrices
> multMM m t =    [[sum (zipWith (*) (head m)(a)) ] ]where  a = [head a | a<-
> t]
>
>
> Main> multMM [[2,1,-6],[1,-3,2]] [[1,0,-3],[0,4,20],[-2,1,1]]
> [[14.0]]
>
> from this i could get only the first multiplication 14    that is by  2*1 +
> 1*0 + -6*-2 = 14
>
> how can i make this go throw all rows and colums to get multiple of matrixs?
>
> Thank you~
>
>
> _______________________________________________