Update dry.md (#181)

* Update dry.md

* Update dry.md

---------

Co-authored-by: YangQi <[email protected]>

Author: fake-rick

src/macros/dry.md

@@ -7,18 +7,18 @@ use std::ops::{Add, Mul, Sub};
 
 macro_rules! assert_equal_len {
     // `tt`（token tree，标记树）指示符表示运算符和标记。
-    ($a:ident, $b: ident, $func:ident, $op:tt) => (
+    ($a:ident, $b: ident, $func:ident, $op:tt) => {
         assert!($a.len() == $b.len(),
                 "{:?}: dimension mismatch: {:?} {:?} {:?}",
                 stringify!($func),
                 ($a.len(),),
                 stringify!($op),
                 ($b.len(),));
-    )
+    };
 }
 
 macro_rules! op {
-    ($func:ident, $bound:ident, $op:tt, $method:ident) => (
+    ($func:ident, $bound:ident, $op:tt, $method:ident) => {
         fn $func<T: $bound<T, Output=T> + Copy>(xs: &mut Vec<T>, ys: &Vec<T>) {
             assert_equal_len!(xs, ys, $func, $op);
 
@@ -27,7 +27,7 @@ macro_rules! op {
                 // *x = x.$method(*y);
             }
         }
-    )
+    };
 }
 
 // 实现 `add_assign`、`mul_assign` 和 `sub_assign` 等函数。