I am new to Haskell and also in programming. I'm trying to learn Haskell with exercises already done.
Just now I get an error that says the following.
error: parse error on input "n", failed modules load: none
From the following code
listaMatriz :: Num a => [[a]] -> Matriz a
listaMatriz xss = listArray ((1,1),(m,n)) (concat xss)
where m = length xss
n = length (head xss)
What do you think is the problem? I can not identify it.
It's a problem of indentation. In Haskell, indentation defines where a block of code begins and ends. Everything you want to define within where must have an indentation greater than this.
listaMatriz :: Num a => [[a]] -> Matriz a
listaMatriz xss = listArray ((1,1),(m,n)) (concat xss)
where
m = length xss
n = length (head xss)
On the other hand, although it is not usual, you can use keys {} and semicolons ; to define the blocks independently of the indentation:
listaMatriz :: Num a => [[a]] -> Matriz a
listaMatriz xss = listArray ((1,1),(m,n)) (concat xss)
where {
m = length xss;
n = length (head xss)
}
You can find more information about these common errors in the wiki .
The problem is in the second line (it should start at the same height as the first one), where is well indented.
listaMatriz :: Num a => [[a]] -> Matriz a
listaMatriz xss = listArray ((1,1),(m,n)) (concat xss)
where m = length xss
n = length (head xss)