CODEWITHSUNDEEP
haskell
user3741052
user3741052

Reputation:

how to generate a matrix of letters in haskell

the user has to type the dimension (it's a quadractic matrix) and random letters will be generated. Ex.: generateMatrix 3

[('a', 'f', 'j'), ('t', 'a', 'b'), ('c', 'y', 'k')]

Each tuple is a line

Upvotes: 0

Views: 372

Answers (2)

ThreeFx
ThreeFx

Reputation: 7360

Using tuples this is impossible without manually hardcoding the solution, which is why the easiest is using lists of lists to represent the matrix if the dimension should be variable.

You could then try something like this:

import System.Random

genMatrix n = format n n (take (n*n) (randomRs ('a','z') (mkStdGen (n*n))))
  where
    format _ 0 _ = []
    format n m text = (take n text) : format n (m-1) (drop n text)

genMatrix gets the number of rows and columns and a "random" string which is then formatted by format. It just splits the list into parts of length n and conses them onto an empty list.

Example:

*Main> genMatrix 3
["nmq","jfj","oih"]

Upvotes: 1

djfoote
djfoote

Reputation: 141

Achieving the randomness you're looking for is no small task for a beginner, but assuming you know the basics of Haskell, LYAH's section on randomness should help you out a lot.

http://learnyouahaskell.com/input-and-output#randomness

In particular, you may find the randomRs function useful:

ghci> take 10 $ randomRs ('a','z') (mkStdGen 3) :: [Char]
"ndkxbvmomg"

But in order to use that in an application successfully, there's much more you should know about randomness in Haskell and dealing with impurity, so you really should read the whole section.

Another thing to note about your problem is that [(Char, Char, Char)] and [(Char, Char, Char, Char)] are different types, so there's no simple way to have a single function return lists of tuples that are different lengths depending on the input size. For what you're doing, you probably want a list of lists.

Upvotes: 5

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