feat: add support for comments

src/lexer.rs

@@ -57,7 +57,14 @@ impl Lexer {
                     tok = Token::Bang;
                 }
             },
-            '/' => tok = Token::Slash,
+            '/' => {
+                if self.peek_char() == '/' {
+                    self.eat_complete_line();
+                    tok = Token::Comment;
+                } else {
+                    tok = Token::Slash;
+                }
+            },
             '*' => tok = Token::Asterisk,
             '<' => tok = Token::Lt,
             '>' => tok = Token::Gt,
@@ -117,6 +124,12 @@ impl Lexer {
             self.read_char();
         }
     }
+
+    fn eat_complete_line(&mut self) {
+        while self.ch != '\n' && self.ch != '\0' {
+            self.read_char();
+        }
+    }
 }
 
 /// Helper method to check if a char is a letter

src/token.rs

@@ -37,6 +37,8 @@ pub enum Token {
     If,       // if
     Else,     // else
     Return,   // return
+
+    Comment,  // //
 }
 
 pub fn lookup_ident(ident: &str) -> Token {

tests/lexer_test.rs

@@ -13,10 +13,14 @@ fn test_next_token() {
             x + y
         };
 
+        // One line comment
+
         let result = add(five, ten);
         !-/*5;
         5 < 10 > 5;
 
+        // Multi-line
+        // comment
         if (5 < 10) {
             return true;
         } else {
@@ -25,7 +29,7 @@ fn test_next_token() {
 
         10 == 10;
         10 != 9;
-    ";
+        // Comment at the end";
 
     let tests = [
         Token::Let,
@@ -53,6 +57,7 @@ fn test_next_token() {
         Token::Ident("y".to_string()),
         Token::Rbrace,
         Token::Semicolon,
+        Token::Comment,
         Token::Let,
         Token::Ident("result".to_string()),
         Token::Assign,
@@ -75,6 +80,8 @@ fn test_next_token() {
         Token::Gt,
         Token::Int("5".to_string()),
         Token::Semicolon,
+        Token::Comment,
+        Token::Comment,
         Token::If,
         Token::Lparen,
         Token::Int("5".to_string()),
@@ -100,6 +107,7 @@ fn test_next_token() {
         Token::Noteq,
         Token::Int("9".to_string()),
         Token::Semicolon,
+        Token::Comment,
         Token::Eof,
     ];