# Thread: Haskell Matrix Question NEED HELP!

1. ## Haskell Matrix Question NEED HELP!

hi I have a question about haskell coding.

Matrices

One of many ways to define matrices in Haskell is the list of matrix rows, where a row is a list of double precision oating point numbers:

type Matrix=[[Double]]
Using this type you should define the following functions (definition of dim is given as an inspirational example).

dim :: Matrix -> (Int,Int) --returns matrix dimension (number of rows and columns)
dim m = if (not.isMatrix) m then error "Not a matrix" else (length m, length (head m))

isMatrix :: Matrix -> Bool --checks whether all rows have the same length
isMatrix m = and [length (head m) == length a | a <- m]
I have done upto here and I am stuck on multSM.

multSM :: Double -> Matrix -> Matrix --multiplies a scalar and a matrix
when I do:

multSM d m = [[(b*a)| b<-[d], a<-(head m)]] or [map (*d) (head m)]
...I get (using Hugs):

Main> multSM 3 [[2,3,4],[1,3,4],[6,3,0]]
[[6.0,9.0,12.0]]
So I solve 3 [2,3,4] but I do not know how to get the rest 3 [[1,3,4],[6,3,0].

These are rest of unsolved questions if anyone can help with:

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