add support for ++ and +=

src/scanner.zig

@@ -229,6 +229,23 @@ pub const Scanner = struct {
         );
     }
 
+    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;
@@ -255,26 +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();