Quick coding challenge - find all horizontal rectangles formed given a list of points

RectangleFinder.hs

module RectangleFinder where

import           Prelude         hiding ((*))
import qualified Data.Map as Map

type Point = (Int, Int)

countRects :: [Point] -> Int
countRects pts = fst $ foldl processPoints (0, Map.empty) $ filter isAbove $ pts * pts

(*) :: [a] -> [b] -> [(a, b)]
(*) xs ys = [(x,y) | x <- xs, y <- ys]

isAbove :: (Point, Point) -> Bool
isAbove ((x1, y1), (x2, y2)) = y1 > y2 && x1 == x2

processPoints :: (Int, Map.Map (Int, Int) Int) -> (Point, Point) -> (Int, Map.Map (Int, Int) Int)
processPoints (n, m) (p1, p2) = (n + currentValue, Map.insert (snd p1, snd p2) (currentValue + 1) m)
    where
        currentValue :: Int
        currentValue = Map.findWithDefault 0 (snd p1, snd p2) m

testPlain1 :: [Point]
testPlain1 = [
    (0,2), (1,2), (2,2),
    (0,1), (1,1), (2,1),
    (0,0), (1,0), (2,0)]

testPlain2 :: [Point]
testPlain2 = [
    (0,1), (1,1), (2,1),
    (0,0), (1,0), (2,0)]