advance module

Author: NTP-996

syllabus/module/2.3-slides.md

@@ -509,4 +509,17 @@ impl Demo {
 
 ## macro_rules Transcribers
 
+```rust
+// macro_rules transcribers
+macro_rules! demo {
+    () => {
+        println!("{}", format!("demo{}", '!'));
+    };
+}
+
+demo!();
+```
+
+---
+
 

syllabus/module/2.4-slides.md

@@ -4,3 +4,119 @@ description: "Common design patterns in Rust"
 duration: 30 minutes
 ---
 
+## Overlapping Patterns
+
+- Patterns easily overlap.
+- Minimize number of match arms to avoid bugs
+
+```rust
+match slice {
+    [first, ..] => (),
+    [.., last] => (),
+    [] => (),
+}
+
+```
+
+Second arm always ignored
+
+---
+
+## Prevent Overlapping Patterns
+
+- Match the largest patterns first, followed by smaller patterns
+
+```rust
+match slice {
+    [] => (),
+    [a, ..] => (),
+    [a, b, ..] => (),
+    [a, b, c, ..] => (),
+    [a, b, c, d, ..] => (),
+}
+// "First two arms cover all cases, remaining will be ignored"
+match slice {
+    [a, b, c, d, ..] => (),
+    [a, b, c, ..] => (),
+    [a, b, ..] => (),
+    [a, ..] => (),
+    [] => (),
+}
+// "All arms can be matched"
+
+```
+
+---
+
+## Guards
+
+```rust
+let nums = vec![7, 8, 9];
+match nums.as_slice() {
+    [first @ 1..=3, rest @ ..] => {
+        // 'first' is always 1, 2 or 3
+        // 'rest' is the remaining slice
+    },
+    [single] if single == &5 || single == &6 => (),
+    [a, b] => (),
+    [..] => (),
+    [] => (),
+}
+```
+
+## Typestates Patterns
+
+- Leverage type system to encode state changes
+- Implemented by creating a type for each state
+  - Use move semantics to invalidate a state
+  - Return next state from previous state
+  - Optionally drop the state
+    - Close file, connection dropped, etc
+  - Compile time enforcement of logic
+
+---
+
+## Example
+
+```rust
+struct BusTicket;
+struct BoardedBusTicket;
+
+impl BusTicket {
+    fn board(self) -> BoardedBusTicket {
+        BoardedBusTicket
+    }
+}
+
+let ticket = BusTicket;
+let boarded = ticket.board();
+
+// Compile error
+ticket.board();
+```
+
+---
+
+## Example
+
+```rust
+struct File<'a>(&'a str);
+
+impl<'a> File<'a> {
+    fn read_bytes(&self) -> Vec<u8> {
+        // ... read data ...
+    }
+
+    fn delete(self) {
+        // ... delete file ...
+    }
+}
+
+let file = File("data.txt");
+let data = file.read_bytes();
+file.delete();
+
+// Compile error
+let read_again = file.read_bytes();
+
+```