CODEWITHSUNDEEP
listhaskellinteger
DonnumS
DonnumS

Reputation: 316

Find index of largest Integer

I'm dabbling in some Haskell and have stumbled upon a bump in the road

I want to write a function that an AI uses to choose a row in a simple board game. The board in said game is represented by a list of integers. Like this:

board = [1,2,3,4,5]

The index + 1 of the numbers in the row on the board and the Int itself is the number of pieces left on said row. How I aim to make this function work is by first to find the largest number in the list and then return (index + 1) of this number in the form of an IO Int.

This is where I'm struggling since I can't seem to find any good answer to this online

This is what I'm working with so far:

-- Returns index of row with largest number along the number itself
aiHelper :: Board -> (Int, Int)
aiHelper xs = maximumBy (comparing fst) (zip xs [1..])

-- Returns row with largest number as IO Int
aiRow :: Board -> IO Int
aiRow xs = do
              let y = snd $ aiHelper xs
              return $ y

I'm not quite sure if this code does what I'm looking for, and is there an easier and cleaner solution to my code?

Upvotes: 2

Views: 118

Answers (2)

Mark Seemann
Mark Seemann

Reputation: 233135

You can simplify the code like this:

aiRow :: Board -> IO Int
aiRow xs = return $ snd $ aiHelper xs

Or, by making an Eta reduction, to this:

aiRow :: Board -> IO Int
aiRow = return . snd . aiHelper

But, really, you don't need to return IO Int. Why not just the following?

aiRow :: Board -> Int
aiRow = snd . aiHelper

At this point, however, you're probably below the Fairbairn threshold.

Upvotes: 5

sshine
sshine

Reputation: 16105

After Mark's proposal, aiRow now does so little on its own that you might as well combine it with aiHelper:

maximumIndex :: Ord a => [a] -> Int
maximumIndex = fst . maximumBy (comparing snd) . zip [1..]

(Switching fst and snd.)

Upvotes: 1

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