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-- Test grouping with both a using and a by clause
{-# OPTIONS_GHC -XTransformListComp #-}
module Main where
import Data.List(groupBy)
import GHC.Exts(the)
groupRuns :: Eq b => (a -> b) -> [a] -> [[a]]
groupRuns f = groupBy (\x y -> f x == f y)
main = putStrLn (show output)
where
output = [ (the x, product y)
| x <- ([1, 1, 1, 2, 2, 1, 3])
, y <- [4..6]
, then group by x using groupRuns ]
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