WIP

yarn-project/foundation/src/fields/fields.ts

@@ -282,16 +282,17 @@ export class Fr extends BaseField {
 
   /**
    * Computes the square root of the field element.
-   * @returns The square root of the field element if it exists (undefined if not).
+   * @returns The square root of the field element (null if it does not exist).
    */
-  sqrt(): Fr | undefined {
+  sqrt(): Fr | null {
     const wasm = BarretenbergSync.getSingleton().getWasm();
     wasm.writeMemory(0, this.toBuffer());
     wasm.call('grumpkin_fr_sqrt', 0, Fr.SIZE_IN_BYTES);
     const isSqrtBuf = Buffer.from(wasm.getMemorySlice(Fr.SIZE_IN_BYTES, Fr.SIZE_IN_BYTES + 1));
     const isSqrt = isSqrtBuf[0] === 1;
     if (!isSqrt) {
-      return undefined;
+      // Field element is not a quadratic residue mod p so it has no square root.
+      return null;
     }
 
     const rootBuf = Buffer.from(wasm.getMemorySlice(Fr.SIZE_IN_BYTES + 1, Fr.SIZE_IN_BYTES * 2 + 1))

yarn-project/foundation/src/fields/point.ts

@@ -87,11 +87,8 @@ export class Point {
    * @returns The point as an array of 2 fields
    */
   static fromXAndSign(x: Fr, sign: boolean) {
-    // Define the constant A for the Grumpkin curve equation (y^2 = x^3 - A)
-    const A = new Fr(17);
-
     // Calculate y^2 = x^3 - 17
-    const ySquared = x.square().mul(x).sub(A);
+    const ySquared = x.square().mul(x).sub(new Fr(17));
 
     // Calculate the square root of ySquared
     const y = ySquared.sqrt();