Data commit

Task/Isqrt-integer-square-root-of-X/Haskell/isqrt-integer-square-root-of-x.hs

@@ -0,0 +1,15 @@
+import Data.Bits
+
+isqrt :: Integer -> Integer
+isqrt n = go n 0 (q `shiftR` 2)
+ where
+   q = head $ dropWhile (< n) $ iterate (`shiftL` 2) 1
+   go z r 0 = r
+   go z r q = let t = z - r - q
+              in if t >= 0
+                 then go t (r `shiftR` 1 + q) (q `shiftR` 2)
+                 else go z (r `shiftR` 1) (q `shiftR` 2)
+
+main = do
+  print $ isqrt <$> [1..65]
+  mapM_ print $ zip [1,3..73] (isqrt <$> iterate (49 *) 7)