Improve code quality

Author: ChJR

common/src/float_ops.rs

@@ -149,11 +149,7 @@ fn remove_trailing_zeros(s: String) -> String {
 pub fn format_general(precision: usize, magnitude: f64, case: Case) -> String {
     match magnitude {
         magnitude if magnitude.is_finite() => {
-            let prec = match precision {
-                0 => 0,
-                _ => precision - 1,
-            };
-            let r_exp = format!("{:.*e}", prec, magnitude);
+            let r_exp = format!("{:.*e}", precision.saturating_sub(1), magnitude);
             let mut parts = r_exp.splitn(2, 'e');
             let base = parts.next().unwrap();
             let exponent = parts.next().unwrap().parse::<i64>().unwrap();

vm/src/builtins/pystr.rs

@@ -180,11 +180,7 @@ impl PyIter for PyStrReverseIterator {
                     break;
                 }
             }
-            if end < 4 {
-                start.unwrap_or(0)
-            } else {
-                start.unwrap_or(end - 4)
-            }
+            start.unwrap_or_else(|| end.saturating_sub(4))
         };
 
         let stored = zelf.position.swap(start);