[Haskell-beginners] Matrix and types

[Francesco Ariis]

Hello Mike,

On Thu, Mar 14, 2019 at 11:10:06AM +0000, mike h wrote:
> Multiplication of two matrices is only defined when the the number of columns in the first matrix 
> equals the number of rows in the second matrix. i.e. c1 == r2
> 
> So when writing the multiplication function I can check that  c1 == r2 and do something.
> However what I really want to do, if possible, is to have the compiler catch the error. 

Type-level literals [1] or any kind of similar trickery should help you
with having matrices checked at compile-time.

[1] https://downloads.haskell.org/~ghc/7.10.1/docs/html/users_guide/type-level-literals.html