grumpkin point contract

contracts/libs/Grumpkin.sol

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+// This file is MIT Licensed.
+pragma solidity ^0.8.0;
+
+library Grumpkin {
+    struct Point {
+        uint X;
+        uint Y;
+    }
+
+    /// Check if point is valid.
+    function isOnCurve(
+            Point memory a
+    ) internal view returns (bool) {
+        uint r = 21888242871839275222246405745257275088548364400416034343698204186575808495617;
+
+        // Y^2 = X^3 - 17
+        uint y2 = mulmod(a.Y, a.Y, r);
+        uint z = addmod(y2, 17, r);
+        uint x2 = mulmod(a.X, a.X, r);
+        uint x3 = mulmod(a.X, x2, r);
+
+        return z == x3;
+    }
+}