using solditiy max function to get the max value (#196)

Author: aalavandhan

contracts/UFragments.sol

@@ -58,15 +58,15 @@ contract UFragments is ERC20Detailed, Ownable {
     }
 
     uint256 private constant DECIMALS = 9;
-    uint256 private constant MAX_UINT256 = ~uint256(0);
+    uint256 private constant MAX_UINT256 = type(uint256).max;
     uint256 private constant INITIAL_FRAGMENTS_SUPPLY = 50 * 10**6 * 10**DECIMALS;
 
     // TOTAL_GONS is a multiple of INITIAL_FRAGMENTS_SUPPLY so that _gonsPerFragment is an integer.
     // Use the highest value that fits in a uint256 for max granularity.
     uint256 private constant TOTAL_GONS = MAX_UINT256 - (MAX_UINT256 % INITIAL_FRAGMENTS_SUPPLY);
 
     // MAX_SUPPLY = maximum integer < (sqrt(4*TOTAL_GONS + 1) - 1) / 2
-    uint256 private constant MAX_SUPPLY = ~uint128(0); // (2^128) - 1
+    uint256 private constant MAX_SUPPLY = type(uint128).max; // (2^128) - 1
 
     uint256 private _totalSupply;
     uint256 private _gonsPerFragment;

contracts/UFragmentsPolicy.sol

@@ -83,7 +83,7 @@ contract UFragmentsPolicy is Ownable {
     // Both are 18 decimals fixed point numbers.
     uint256 private constant MAX_RATE = 10**6 * 10**DECIMALS;
     // MAX_SUPPLY = MAX_INT256 / MAX_RATE
-    uint256 private constant MAX_SUPPLY = ~(uint256(1) << 255) / MAX_RATE;
+    uint256 public constant MAX_SUPPLY = uint256(type(int256).max) / MAX_RATE;
 
     // This module orchestrates the rebase execution and downstream notification.
     address public orchestrator;