display for ast

CHANGELOG.md

 # Changelog for the repository
 
+## 2020-09-03
+- Updated ast with Display
+
 ## 2020-09-03
 - Added src/comment 
     - single and multiline comments

src/ast/ast.rs

+use std::fmt;
+
 // ast
 
+// println!("{:?}", ..)
 #[derive(Debug)] 
 pub enum NumOrId {
     Num(usize),
     Id(String),
 }
+
+// println!("{}", ..)
+impl fmt::Display for NumOrId {
+
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            NumOrId::Num(i) => write!(f, "{}", i)?,
+            NumOrId::Id(s) => write!(f, "{}", s)?,
+        };
+        Ok(())
+    }
+}
\ No newline at end of file

src/ast/main.rs

@@ -10,10 +10,13 @@ fn main() {
     println!("minimal");
     println!("{:?}", NumOrIdParser::new().parse("123"));
     println!("{:?}", NumOrIdParser::new().parse("a1_a"));
+
+    println!("{}", NumOrIdParser::new().parse("123").unwrap());
+    println!("{}", NumOrIdParser::new().parse("a1_a").unwrap());
 }
 
 #[test]
 fn parse_num_or_id() {
-    // println!("{:?}", NumOrIdParser::new().parse("123"));
-    // println!("{:?}", NumOrIdParser::new().parse("a1_a"));
+   assert_eq!(format!("{}", NumOrIdParser::new().parse("123").unwrap()), "123");
+   assert_eq!(format!("{}", NumOrIdParser::new().parse("a1_a").unwrap()), "a1_a");
 }