doc: update book 06_01_arrays (#195)

book/src/06_ticket_management/01_arrays.md

@@ -21,6 +21,15 @@ let numbers: [u32; 3] = [1, 2, 3];
 This creates an array of 3 integers, initialized with the values `1`, `2`, and `3`.\
 The type of the array is `[u32; 3]`, which reads as "an array of `u32`s with a length of 3".
 
+If all array elements are the same, you can use a shorter syntax to initialize it:
+
+```rust
+// [ <value> ; <number of elements> ]
+let numbers: [u32; 3] = [1; 3];
+```
+
+`[1; 3]` creates an array of three elements, all equal to `1`.
+
 ### Accessing elements
 
 You can access elements of an array using square brackets: