Binary search in Haskell

program/program/implement-binary-search/implement_binary_search.hs

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+-- Binary search function
+binarySearch :: (Ord a) => [a] -> a -> Int
+binarySearch arr x = binarySearchHelper arr x 0 (length arr - 1)
+
+-- Helper function to perform the binary search
+binarySearchHelper :: (Ord a) => [a] -> a -> Int -> Int -> Int
+binarySearchHelper arr x lowerBound upperBound
+  | upperBound < lowerBound = -1  -- x does not exist
+  | arr !! midPoint < x      = binarySearchHelper arr x (midPoint + 1) upperBound
+  | arr !! midPoint > x      = binarySearchHelper arr x lowerBound (midPoint - 1)
+  | otherwise                = midPoint  -- x found at midPoint
+  where
+    midPoint = lowerBound + (upperBound - lowerBound) `div` 2
+
+-- Example usage
+main :: IO ()
+main = do
+    let arr = [2, 3, 4, 10, 40]
+    let x = 10
+    let result = binarySearch arr x
+    if result /= -1
+        then putStrLn $ "Element " ++ show x ++ " is present at index " ++ show result
+        else putStrLn $ "Element " ++ show x ++ " is not present in array"