better debug for RD

utils/calendrical_calculations/src/rata_die.rs

@@ -8,6 +8,7 @@
 // package root or at http://www.apache.org/licenses/LICENSE-2.0.
 
 use core::ops::{Add, AddAssign, Sub, SubAssign};
+use core::fmt;
 #[allow(unused_imports)]
 use core_maths::*;
 
@@ -17,7 +18,7 @@ use core_maths::*;
 ///
 /// It is a logic error to construct a RataDie
 /// except from a date that is in range of one of the official calendars.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
 pub struct RataDie(i64);
 
 impl RataDie {
@@ -75,6 +76,18 @@ impl RataDie {
     }
 }
 
+impl fmt::Debug for RataDie {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+
+            let rd = self.0;
+        if let Ok((y, m, d)) = crate::iso::iso_from_fixed(*self) {
+            write!(f, "{rd} R.D. ({y}-{m:02}-{d:02})")
+        } else {
+            write!(f, "{rd} R.D. (out of bounds)")
+        }
+    }
+}
+
 /// Shift a RataDie N days into the future
 impl Add<i64> for RataDie {
     type Output = Self;