add chapter [Docs and Comments]

practices/doc-comments/src/compute.rs

@@ -0,0 +1,36 @@
+//! Do some complicated arithmetic that you can't do by yourself
+
+/// # Panics
+///
+/// The function panics if the second argument is zero.
+///
+/// ```rust,should_panic
+/// // panics on division by zero
+/// doc_comments::compute::div(10, 0);
+/// ```
+pub fn div(a: i32, b: i32) -> i32 {
+    if b == 0 {
+        panic!("Divide-by-zero error");
+    }
+
+    a / b
+}
+
+
+/// ```
+/// # fn try_main() -> Result<(), String> {
+/// let res = doc_comments::compute::try_div(10, 1)?;
+/// # Ok(()) // returning from try_main
+/// # }
+/// # fn main() {
+/// #    try_main().unwrap();
+/// #
+/// # }
+/// ```
+pub fn try_div(a: i32, b: i32) -> Result<i32, String> {
+    if b == 0 {
+        Err(String::from("Divide-by-zero"))
+    } else {
+        Ok(a / b)
+    }
+}