-- dupos.hs: duplicates and positions
--
-- Copyright (C) 2021-2025 Rudy Matela
-- Distributed under the 3-Clause BSD licence (see the file LICENSE).
import Conjure
import Test.LeanCheck -- needed for duplicatesSpec only
duplicates :: [Int] -> [Int] -- Eq a => [a] -> [a]
duplicates [] = []
duplicates (x:xs) =
if x `elem` xs && not (x `elem` d)
then x : d
else d
where
d = duplicates xs
duplicates' :: [Int] -> [Int]
duplicates' [0,0] = [0]
duplicates' [0,1] = []
duplicates' [1,0,1] = [1]
duplicates' [0,1,0,1] = [0,1]
duplicates' [1,0,1,0,1] = [0,1]
duplicates' [0,1,2,1] = [1]
duplicatesSpec :: ([Int] -> [Int]) -> Bool
duplicatesSpec duplicates = and
[ holds 360 $ \x xs -> (count (x ==) xs > 1) == elem x (duplicates xs)
, holds 360 $ \x xs -> count (x ==) (duplicates xs) <= 1
] where count p = length . filter p
positionsFrom :: Int -> Int -> [Int] -> [Int]
positionsFrom n x = from n
where
from _ [] = []
from n (y:ys) = if y == x
then n : f
else f
where
f = from (n+1) ys
-- this is what conjure _can_ generate
positionsFrom' :: Int -> A -> [A] -> [Int]
positionsFrom' _ _ [] = [] -- 1
positionsFrom' n x (y:ys) = if y == x -- 4
then n : positionsFrom' (n+1) x ys -- 12
else positionsFrom' (n+1) x ys -- 18
main :: IO ()
main = do
-- duplicates [] = [] -- 1
-- duplicates (x:xs) = if x `elem` xs && not (x `elem` duplicates xs) -- 11
-- then x : duplicates xs -- 15
-- else duplicates xs -- 17
-- within reach performance wise.
conjureWith args{maxSize=18} "duplicates" duplicates'
[ pr ([] :: [Int])
, prim "not" not
, prim "&&" (&&)
, prim ":" ((:) :: Int -> [Int] -> [Int])
, prim "elem" (elem :: Int -> [Int] -> Bool)
, prif (undefined :: [Int])
]
conjureFromSpecWith args{maxSize=18} "duplicates" duplicatesSpec
[ pr ([] :: [Int])
, prim "not" not
, prim "&&" (&&)
, prim ":" ((:) :: Int -> [Int] -> [Int])
, prim "elem" (elem :: Int -> [Int] -> Bool)
, prif (undefined :: [Int])
]
-- found!
conjureWithMaxSize 14 "positionsFrom" positionsFrom'
[ pr ([] :: [Int])
, pr (1 :: Int)
, prim "+" ((+) :: Int -> Int -> Int)
, prim ":" ((:) :: Int -> [Int] -> [Int])
, prim "==" ((==) :: A -> A -> Bool)
-- , prif (undefined :: [Int])
-- cheat codes:
, prim "id" (id :: [Int] -> [Int])
, prif (undefined :: [Int] -> [Int])
]