Handle single and multi line comments

src/lexer.rs

@@ -52,6 +52,7 @@ impl<'a> Iterator for Lexer<'a> {
             '{' => symbol!(self, OpenBrace),
             '*' => symbol!(self, Mul),
             '}' => symbol!(self, CloseBrace),
+            '/' => self.lex_forward_slash(),
             '%' => {
                 self.buf.next();
                 self.pos.next_char();
@@ -117,6 +118,27 @@ impl<'a> Lexer<'a> {
         }
     }
 
+    fn lex_forward_slash(&mut self) -> TokenKind {
+        self.buf.next();
+        self.pos.next_char();
+        match self.buf.peek().expect("expected something after '/'") {
+            '/' => {
+                self.buf.by_ref().skip_while(|x| x != &'\n').count();
+            }
+            '*' => {
+                while let Some(tok) = self.buf.next() {
+                    if tok == '*' {
+                        if self.buf.next() == Some('/') {
+                            break;
+                        }
+                    }
+                }
+            }
+            _ => return TokenKind::Symbol(Symbol::Div),
+        }
+        TokenKind::Whitespace(Whitespace::Newline)
+    }
+
     fn lex_num(&mut self) -> TokenKind {
         let mut string = String::with_capacity(99);
         while let Some(c) = self.buf.peek() {