fixing bug in the assembler; it didn't see the target from PushControlFrame

assemble.rkt

@@ -171,7 +171,7 @@ EOF
                         [(PopEnvironment? stmt)
                          empty]
                         [(PushControlFrame? stmt)
-                         empty]
+                         (list (PushControlFrame-label stmt))]
                         [(PopControlFrame? stmt)
                          empty])
                       (loop (rest stmts))))]))))

runtime.js

@@ -99,6 +99,14 @@ var Primitives = (function() {
 	'null?': function(arity, returnLabel) {
 	    var firstArg = MACHINE.env[MACHINE.env.length-1];
 	    return firstArg === NULL;
+	},
+	'add1': function(arity, returnLabel) {
+	    var firstArg = MACHINE.env[MACHINE.env.length-1];
+	    return firstArg + 1;
+	},
+	'sub1': function(arity, returnLabel) {
+	    var firstArg = MACHINE.env[MACHINE.env.length-1];
+	    return firstArg - 1;
 	}
     };
 })();