Merge pull request #1797 from o1-labs/fix/mod-int64

Fix Int64 mod v2

CHANGELOG.md

@@ -17,6 +17,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased](https://github.com/o1-labs/o1js/compare/d6abf1d97...HEAD)
 
+### Fixes
+
+- Fix behavior of `Int64.modV2()` when the input is negative and the remainder should be 0 https://github.com/o1-labs/o1js/pull/1797
+
 ## [1.6.0](https://github.com/o1-labs/o1js/compare/1ad7333e9e...d6abf1d97) - 2024-07-23
 
 ### Added

src/lib/provable/int.ts

@@ -1147,14 +1147,22 @@ class Int64 extends CircuitValue implements BalanceChange {
     return Int64.create(UInt64.from(obj.magnitude), Sign.fromValue(obj.sgn));
   }
 
+  /**
+   * Turns the {@link Int64} into a {@link BigInt}.
+   */
+  toBigint() {
+    let abs = this.magnitude.toBigInt();
+    let sgn = this.sgn.isPositive().toBoolean() ? 1n : -1n;
+    return sgn * abs;
+  }
+
   /**
    * Turns the {@link Int64} into a string.
    */
   toString() {
-    let abs = this.magnitude.toString();
-    let sgn = this.isPositive().toBoolean() || abs === '0' ? '' : '-';
-    return sgn + abs;
+    return this.toBigint().toString();
   }
+
   isConstant() {
     return this.magnitude.value.isConstant() && this.sgn.isConstant();
   }
@@ -1334,7 +1342,11 @@ class Int64 extends CircuitValue implements BalanceChange {
     let isNonNegative = this.magnitude
       .equals(UInt64.zero)
       .or(this.sgn.isPositive());
-    rest = Provable.if(isNonNegative, rest, y_.value.sub(rest));
+    rest = Provable.if(
+      isNonNegative.or(rest.equals(0)),
+      rest,
+      y_.value.sub(rest)
+    );
     return new Int64(new UInt64(rest.value));
   }