tweak math

contracts/libraries/Math.sol

@@ -1,16 +1,16 @@
 pragma solidity 0.5.13;
 
 library Math {
-    function add512(uint x0, uint64 x1, uint y0, uint64 y1) internal pure returns (uint z0, uint64 z1) {
-        assembly {
+    function add512(uint x0, uint x1, uint y0, uint y1) internal pure returns (uint z0, uint z1) {
+        assembly { // solium-disable-line security/no-inline-assembly
             z0 := add(x0, y0)
             z1 := add(add(x1, y1), lt(z0, x0))
         }
     }
-    function mul512(uint x, uint64 y) internal pure returns (uint z0, uint64 z1) {
-        assembly {
-            let mm := mulmod(x, y, not(0))
+    function mul512(uint x, uint y) internal pure returns (uint z0, uint z1) {
+        assembly { // solium-disable-line security/no-inline-assembly
             z0 := mul(x, y)
+            let mm := mulmod(x, y, not(0))
             z1 := sub(sub(mm, z0), lt(mm, z0))
         }
     }
@@ -19,14 +19,14 @@ library Math {
         return x <= y ? x : y;
     }
 
-    function sqrt(uint x) internal pure returns (uint y) {
-        if (x == 0) return 0;
-        else if (x <= 3) return 1;
-        uint z = (x + 1) / 2;
-        y = x;
-        while (z < y) {
-            y = z;
-            z = (x / z + z) / 2;
+    function sqrt(uint y) internal pure returns (uint z) {
+        if (y == 0) return 0;
+        else if (y <= 3) return 1;
+        uint x = (y + 1) / 2;
+        z = y;
+        while (x < z) {
+            z = x;
+            x = (y / x + x) / 2;
         }
     }
 }