Add ANTLR grammar for greetings and farewells with corresponding parser and listener implementations

TreesUser.py

@@ -0,0 +1,27 @@
+from antlr4.Utils import escapeWhitespace
+from antlr4.tree.Tree import Tree
+from antlr4.tree.Trees import Trees
+
+# need forward declaration
+Parser  = None
+
+class TreesUser(Trees):
+
+    # Print out a whole tree in prettier form
+    # Based on Trees.toStringTree()
+    # indent is the number of indents to use in the display
+    @classmethod
+    def PrettyPrint(cls, t:Tree, ruleNames:list=None, recog:Parser=None, indent:int=0):
+        # indentation is the indent to actually display
+        indentation = ''
+        for n in range(indent):
+            indentation += '   '
+        if recog is not None:
+            ruleNames = recog.ruleNames
+        s = escapeWhitespace(cls.getNodeText(t, ruleNames), False)
+        retval = indentation + s + "\n"
+        if t.getChildCount()>0:
+            # we have children to deal with
+            for i in range(0, t.getChildCount()):
+                retval += cls.PrettyPrint(t.getChild(i), ruleNames, indent=indent+1)
+        return retval