character error message

fizzbuzz.grsbpl

@@ -1,9 +1,19 @@
-10 factorial 1 goto exit
+1 &i                                # init loop counter
+:start                              # set start label
+@i 100 - not goto finished          # if i is 100, finish
+@i 15 % not goto print_fizz_buzz    # fizzbuzz
+@i 5 % not goto print_buzz          # buzz
+@i 3 % not goto print_fizz          # fizz
+@i nout '\n' out                    # normal number
+:end                                # go back here after printing
+@i 1 + &i                           # increment i
+1 goto start                        # go back to the start
 
-function factorial 1
-dup not goto isZero
-pop dup 1 - factorial * return
-:isZero
-1 pop return
+:print_fizz_buzz
+   "Fizzbuzz\n" out goto end
+:print_fizz
+   "Fizz\n" out goto end
+:print_buzz
+   "Buzz\n" out goto end
 
-:exit pop dup nout
+:finished 0

src/main/java/com/github/nilstrieb/grsbpl/language/Lexer.java

@@ -92,7 +92,7 @@ public class Lexer {
             value = escape();
         }
         add(CHAR, value);
-        consume();
+        expect('\'');
     }
 
     private void string() {
@@ -194,6 +194,13 @@ public class Lexer {
         advance();
     }
 
+    private void expect(char c) {
+        if (peek() != c) {
+            lexException("Excepted character '" + c + "' but found '" + peek() + "'");
+        }
+        advance();
+    }
+
     private char last() {
         return program[position - 1];
     }