From a colleague: GPT Pretty smart(?!). But this is of course simple, and searchable.
Still... -------------------------------------------------------------------------------------------------- GPT-4 when prompted: Write binary search in Haskel. Print results using putStrLn. Ensure bug-free code by specifying preconditions, postconditions, invariants, variants, internal states. gives the following response: -- Binary search in Haskell -- Precondition: the list is sorted in ascending order -- Postcondition: the function returns the index of the target element if found, or Nothing otherwise -- Invariant: the search space is always within the bounds of the list -- Variant: the search space decreases by half at each recursive call -- Internal state: the lower and upper bounds of the search space binarySearch :: Ord a => [a] -> a -> Maybe Int binarySearch xs x = go xs x 0 (length xs - 1) where go xs x lo hi | lo > hi = Nothing -- base case: search space is empty | x == midElem = Just mid -- base case: target element is found | x < midElem = go xs x lo (mid - 1) -- recursive case: search in the left half | otherwise = go xs x (mid + 1) hi -- recursive case: search in the right half where mid = (lo + hi) `div` 2 -- calculate the middle index midElem = xs !! mid -- get the middle element -- Print results using putStrLn main :: IO () main = do let xs = [1, 3, 5, 7, 9] -- a sorted list of integers let x = 5 -- a target element to search for let result = binarySearch xs x -- call the binary search function case result of -- pattern match on the result Nothing -> putStrLn "Element not found" -- print a message if Nothing is returned Just i -> putStrLn $ "Element found at index " ++ show i -- print a message with the index if Just i is returned The above code runs: https://onecompiler.com/cpp/3z48yt2pp [cid:image001.png@01D963E1.B0EB6AB0]
