♻️ Refactor the is_negative Function Into a Proper sign Function (#…

…187)

Signed-off-by: Pascal Marco Caversaccio <[email protected]>

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## [`0.0.5`](https://github.com/pcaversaccio/snekmate/releases/tag/v0.0.5) (Unreleased)
 
+### ♻️ Refactoring
+
+- **Utility Functions**
+  - [`Math`](https://github.com/pcaversaccio/snekmate/blob/v0.0.5/src/utils/Math.vy): Refactor the `is_negative` function into a proper `sign` function that returns the indication of the sign of a 32-byte signed integer. ([#187](https://github.com/pcaversaccio/snekmate/pull/187))
+
 ### 👀 Full Changelog
 
 - [`v0.0.4...v0.0.5`](https://github.com/pcaversaccio/snekmate/compare/v0.0.4...v0.0.5)

src/utils/Math.vy

@@ -13,7 +13,7 @@
         - `uint256_average` (`external` `pure` function),
         - `int256_average` (`external` `pure` function),
         - `ceil_div` (`external` `pure` function),
-        - `is_negative` (`external` `pure` function),
+        - `sign` (`external` `pure` function),
         - `mul_div` (`external` `pure` function),
         - `log_2` (`external` `pure` function),
         - `log_10` (`external` `pure` function),
@@ -92,14 +92,17 @@ def ceil_div(x: uint256, y: uint256) -> uint256:
 
 @external
 @pure
-def is_negative(x: int256) -> bool:
+def sign(x: int256) -> int256:
     """
-    @dev Returns `True` if a 32-byte signed integer is negative.
-    @notice Note that this function returns `False` for 0.
+    @dev Returns the indication of the sign of a 32-byte signed integer.
+    @notice The function returns `-1` if `x < 0`, `0` if `x == 0`, and `1`
+            if `x > 0`. For more details on finding the sign of a signed
+            integer, please refer to:
+            https://graphics.stanford.edu/~seander/bithacks.html#CopyIntegerSign.
     @param x The 32-byte signed integer variable.
-    @return bool The verification whether `x` is negative or not.
+    @return int256 The 32-byte sign indication (`1`, `0`, or `-1`) of `x`.
     """
-    return (x ^ 1 < empty(int256))
+    return unsafe_sub(convert((x > 0), int256), convert((x < 0), int256))
 
 
 @external

test/utils/Math.t.sol

@@ -154,14 +154,16 @@ contract MathTest is Test {
         math.ceil_div(1, 0);
     }
 
-    function testIsNegative() public {
-        assertEq(math.is_negative(0), false);
-        assertEq(math.is_negative(-1), true);
-        assertEq(math.is_negative(-1 * -1), false);
-        assertEq(math.is_negative(-1 * 100), true);
-        assertEq(math.is_negative(0 * -1), false);
-        assertEq(math.is_negative(int256(type(int16).min) * 2), true);
-        assertEq(math.is_negative(type(int256).min + type(int16).max), true);
+    function testSign() public {
+        assertEq(math.sign(0), 0);
+        assertEq(math.sign(-1), -1);
+        assertEq(math.sign(-1 * -1), 1);
+        assertEq(math.sign(-1 * 100), -1);
+        assertEq(math.sign(0 * -1), 0);
+        assertEq(math.sign(int256(type(int16).min) * 2), -1);
+        assertEq(math.sign(int256(type(int16).max) * 2), 1);
+        assertEq(math.sign(type(int256).min + type(int16).max), -1);
+        assertEq(math.sign(type(int256).max - type(int16).max), 1);
     }
 
     function testMulDivDivisionByZero() public {
@@ -482,11 +484,13 @@ contract MathTest is Test {
         }
     }
 
-    function testFuzzIsNegative(int256 x) public {
-        if (x >= 0) {
-            assertEq(math.is_negative(x), false);
+    function testFuzzSign(int256 x) public {
+        if (x > 0) {
+            assertEq(math.sign(x), 1);
+        } else if (x < 0) {
+            assertEq(math.sign(x), -1);
         } else {
-            assertEq(math.is_negative(x), true);
+            assertEq(math.sign(x), 0);
         }
     }
 

test/utils/interfaces/IMath.sol

@@ -11,7 +11,7 @@ interface IMath {
 
     function ceil_div(uint256 x, uint256 y) external pure returns (uint256);
 
-    function is_negative(int256 x) external pure returns (bool);
+    function sign(int256 x) external pure returns (int256);
 
     function mul_div(
         uint256 x,