add support for ++ and +=

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 +204,48 @@ 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],
+        );
+    }
+
+    fn makeTripleMatchToken(
+        self: *Scanner,
+        char1: u8,
+        ttype1: TokenType,
+        char2,
+        ttype2: TokenType,
+        fallback: TokenType,
+    ) Token {
+        if (self.match(char1)) {
+            return self.makeToken(ttype1);
+        } else if (self.match(char2)) {
+            return self.makeToken(ttype2);
+        } else {
+            return self.makeToken(fallback);
+        }
+    }
+
     pub fn nextToken(self: *Scanner) !?Token {
         self.skipWhitespace();
         self.start = self.current;
@@ -224,26 +272,14 @@ pub const Scanner = struct {
             '$' => self.makeToken(.DollarSign),
 
             '-' => self.makeToken(.Minus),
-            '+' => self.makeToken(.Plus),
             '*' => self.makeToken(.Star),
+            '%' => self.makeToken(.Modulo),
 
             '!' => self.makeMatchToken('=', .BangEqual, .Bang),
             '=' => self.makeMatchToken('=', .EqualEqual, .Equal),
-
-            // there can be three tokens from a <
-            //  - <, which is LessThan
-            //  - <=, which is LessEqual
-            //  - <<, which is LeftDoubleChevron
-            '<' => blk: {
-                if (self.match('=')) {
-                    break :blk self.makeToken(.LessEqual);
-                } else if (self.match('<')) {
-                    break :blk self.makeToken(.LeftDoubleChevron);
-                } else {
-                    break :blk self.makeToken(.Less);
-                }
-            },
             '>' => self.makeMatchToken('=', .GreaterEqual, .Greater),
+            '+' => self.makeTripleMatchToken('+', .PlusPlus, '=', .PlusEqual, .Plus),
+            '<' => self.makeTripleMatchToken('=', .LessEqual, '<', .LeftDoubleChevron, .Less),
 
             '/' => blk: {
                 var next = self.peekNext();
@@ -270,6 +306,9 @@ pub const Scanner = struct {
                 }
             },
 
+            '\'' => try self.doString('\''),
+            '"' => try self.doString('"'),
+
             else => return ScannerError.Unexpected,
         };