Add TryInto<u512, u256> (#5031)

Co-authored-by: Marek Kaput <[email protected]> Co-authored-by: Gil Ben-Shachar <[email protected]> Co-authored-by: ilyalesokhin-starkware <[email protected]> Co-authored-by: yuvalsw <[email protected]>
starkware-libs · Feb 14, 2024 · 1ac6771 · 1ac6771
1 parent c20ac70
commit 1ac6771
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diff --git a/corelib/src/integer.cairo b/corelib/src/integer.cairo
@@ -1373,6 +1373,16 @@ extern fn u512_safe_divmod_by_u256(
     U128MulGuarantee
 ) implicits(RangeCheck) nopanic;
 
+impl U512TryIntoU256 of TryInto<u512, u256> {
+    fn try_into(self: u512) -> Option<u256> {
+        if self.limb2 != 0 || self.limb3 != 0 {
+            Option::None
+        } else {
+            Option::Some(u256 { low: self.limb0, high: self.limb1 })
+        }
+    }
+}
+
 /// Bounded
 pub trait BoundedInt<T> {
     #[must_use]

diff --git a/corelib/src/test/integer_test.cairo b/corelib/src/test/integer_test.cairo
@@ -795,6 +795,17 @@ fn test_u512_safe_div_rem_by_u256() {
     assert(r == 0x1e0eb905027d0150d2618bbd71844d50, 'large rem failed');
 }
 
+#[test]
+fn test_u512_try_into_u256() {
+    assert!(
+        u512 { limb0: 1, limb1: 2, limb2: 0, limb3: 0 }
+            .try_into() == Option::Some(0x200000000000000000000000000000001_u256)
+    );
+    assert!(u512 { limb0: 1, limb1: 2, limb2: 3, limb3: 0 }.try_into() == Option::<u256>::None);
+    assert!(u512 { limb0: 1, limb1: 2, limb2: 0, limb3: 4 }.try_into() == Option::<u256>::None);
+    assert!(u512 { limb0: 1, limb1: 2, limb2: 3, limb3: 4 }.try_into() == Option::<u256>::None);
+}
+
 #[test]
 fn test_min() {
     let min_u8: u8 = BoundedInt::min();