add string support

src/scanner.zig

@@ -116,10 +116,16 @@ pub const Scanner = struct {
         };
     }
 
-    fn makeTokenAdvance(self: *Scanner, ttype: TokenType) Token {
-        var tok = self.makeToken(ttype);
-        self.current += 1;
-        return tok;
+    fn makeTokenLexeme(
+        self: *Scanner,
+        ttype: TokenType,
+        lexeme: []const u8,
+    ) Token {
+        return Token{
+            .ttype = ttype,
+            .lexeme = lexeme,
+            .line = self.line,
+        };
     }
 
     /// Check if the next character matches what is expected.
@@ -198,6 +204,31 @@ pub const Scanner = struct {
         return self.makeToken(ttype);
     }
 
+    /// Consume a string. stop_char is used to determine
+    /// if the string is a single quote or double quote string
+    fn doString(self: *Scanner, stop_char: u8) !Token {
+        // consume entire string
+        while (self.peekNext() != stop_char and !self.isAtEnd()) {
+            if (self.peek() == '\n') self.line += 1;
+            _ = self.advance();
+        }
+
+        // unterminated string.
+        if (self.isAtEnd()) {
+            return ScannerError.Unterminated;
+        }
+
+        // the closing character of the string
+        _ = self.advance();
+
+        // remove the starting and ending chars of the string
+        const lexeme = self.currentLexeme();
+        return self.makeTokenLexeme(
+            .String,
+            lexeme[1 .. lexeme.len - 1],
+        );
+    }
+
     pub fn nextToken(self: *Scanner) !?Token {
         self.skipWhitespace();
         self.start = self.current;
@@ -270,6 +301,9 @@ pub const Scanner = struct {
                 }
             },
 
+            '\'' => try self.doString('\''),
+            '"' => try self.doString('"'),
+
             else => return ScannerError.Unexpected,
         };