Add sequence and alternation

grammar_parser.meta

@@ -226,6 +226,37 @@ Not.match(stream, context, actions) {
     }
 }
 
+// Sequence
+
+Sequence = Object.subtype(#Sequence);
+
+Sequence.match(stream, context, actions) {
+    i = 0;
+    match = 1;
+    while (i < self.length() && match == 1) {
+        match = self[i].match(stream, context, actions);
+    }
+    match;
+}
+
+// Alternation
+
+Alternation = Object.subtype(#Alternation);
+
+Alternation.match(stream, context, actions) {
+    i = 0;
+    match = 0;
+    while(i < self.length() && match == 0){
+        initialActionCount = actions.length();
+        match = self[i].match(stream, context, actions);
+        if (match == 0) {
+            while (actions.length() > initialActionCount) {
+                actions.pop();
+            }
+        }
+    }
+}
+
 // Action
 
 Action = Object.subtype(#Action);