Add approxEq function for approximate equality comparison

foundry.lock

@@ -0,0 +1,5 @@
+{
+  "lib/forge-std": {
+    "rev": "f73c73d2018eb6a111f35e4dae7b4f27401e9421"
+  }
+}

src/Asserts.sol

@@ -12,6 +12,10 @@ abstract contract Asserts {
 
     function eq(uint256 a, uint256 b, string memory reason) internal virtual;
 
+    function approxEq(uint256 a, uint256 b, uint256 maxPercentDelta, string memory reason) internal virtual;
+
+    function approxEq(int256 a, int256 b, uint256 maxPercentDelta, string memory reason) internal virtual;
+
     function t(bool b, string memory reason) internal virtual;
 
     function between(uint256 value, uint256 low, uint256 high) internal virtual returns (uint256);

src/CryticAsserts.sol

@@ -41,6 +41,28 @@ contract CryticAsserts is Asserts {
         }
     }
 
+    function approxEq(uint256 a, uint256 b, uint256 maxPercentDelta, string memory message) internal virtual override {
+        if (b == 0) return eq(a, b, message); // If the right is 0, left must be too.
+
+        uint256 diff = a > b ? a - b : b - a;
+        uint256 percentDelta = diff * 1e18 / b;
+
+        gt(maxPercentDelta, percentDelta, message);
+    }
+
+    function approxEq(int256 a, int256 b, uint256 maxPercentDelta, string memory message) internal virtual override {
+        if (b == 0) return t(a == b, message); // If the right is 0, left must be too.
+
+        int256 d = a - b;
+        uint256 diff = d >= 0 ? uint256(d) : uint256(-d);
+        uint256 base = b >= 0 ? uint256(b) : uint256(-b);
+
+        // percentDelta = |a - b| / |b| in 1e18 precision
+        uint256 percentDelta = (diff * 1e18) / base;
+
+        gt(maxPercentDelta, percentDelta, message);
+    }
+
     function t(bool b, string memory reason) internal virtual override {
         if (!b) {
             emit Log(reason);

src/FoundryAsserts.sol

@@ -24,6 +24,14 @@ contract FoundryAsserts is Test, Asserts {
     function eq(uint256 a, uint256 b, string memory reason) internal virtual override {
         assertEq(a, b, reason);
     }
+
+    function approxEq(uint256 a, uint256 b, uint256 maxPercentDelta, string memory message) internal virtual override {
+        assertApproxEqRel(a, b, maxPercentDelta, message);
+    }
+
+    function approxEq(int256 a, int256 b, uint256 maxPercentDelta, string memory message) internal virtual override {
+        assertApproxEqRel(a, b, maxPercentDelta, message);
+    }
 
     function t(bool b, string memory reason) internal virtual override {
         assertTrue(b, reason);

src/HalmosAsserts.sol

@@ -25,6 +25,14 @@ contract HalmosAsserts is Test, Asserts {
         assertEq(a, b, reason);
     }
 
+    function approxEq(uint256 a, uint256 b, uint256 maxPercentDelta, string memory message) internal virtual override {
+        assertApproxEqRel(a, b, maxPercentDelta, message);
+    }
+
+    function approxEq(int256 a, int256 b, uint256 maxPercentDelta, string memory message) internal virtual override {
+        assertApproxEqRel(a, b, maxPercentDelta, message);
+    }
+
     function t(bool b, string memory reason) internal virtual override {
         assertTrue(b, reason);
     }