Merge pull request #7166 from svcxc/rocdec-traits

Implement Default/PartialOrd/Ord for RocDec

crates/roc_std/src/lib.rs

@@ -289,7 +289,7 @@ impl<T, E> Drop for RocResult<T, E> {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Default)]
 #[repr(C, align(16))]
 pub struct RocDec([u8; 16]);
 
@@ -477,6 +477,18 @@ impl fmt::Display for RocDec {
     }
 }
 
+impl PartialOrd for RocDec {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for RocDec {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.as_i128().cmp(&other.as_i128())
+    }
+}
+
 #[repr(C, align(16))]
 #[derive(Clone, Copy, Eq, Default)]
 pub struct I128([u8; 16]);

crates/roc_std/tests/test_roc_std.rs

@@ -307,6 +307,35 @@ mod test_roc_std {
         assert_eq!(format!("{example}"), "3.141592653589793238");
     }
 
+    #[test]
+    fn roc_dec_sort() {
+        let neg_one_point_five = RocDec::from_str("-1.5").unwrap();
+
+        let mut sorted_by_ord = [
+            neg_one_point_five,
+            RocDec::from(35),
+            RocDec::from(-10057),
+            RocDec::from(0),
+        ];
+
+        sorted_by_ord.sort();
+
+        let manually_sorted = [
+            RocDec::from(-10057),
+            neg_one_point_five,
+            RocDec::from(0),
+            RocDec::from(35),
+        ];
+
+        assert_eq!(sorted_by_ord, manually_sorted);
+    }
+
+    #[test]
+    fn roc_dec_default() {
+        // check if derived Default still returns zero if the implementation ever changes
+        assert_eq!(RocDec::from(0), RocDec::default());
+    }
+
     #[test]
     fn safe_send_no_copy() {
         let x = RocStr::from("This is a long string but still unique. Yay!!!");