Antlr4.Analysis.LeftFactoringRuleTransformer.ExpandOptionalQuantifiersForAlt C# (CSharp) Method

ExpandOptionalQuantifiersForAlt() protected method

protected ExpandOptionalQuantifiersForAlt ( GrammarAST alt ) : GrammarAST
alt Antlr4.Tool.Ast.GrammarAST
return Antlr4.Tool.Ast.GrammarAST
        protected virtual GrammarAST ExpandOptionalQuantifiersForAlt(GrammarAST alt)
        {
            if (alt.ChildCount == 0)
            {
                return null;
            }

            if (alt.GetChild(0).Type == ANTLRParser.OPTIONAL)
            {
                GrammarAST root = (GrammarAST)adaptor.Nil();

                GrammarAST alt2 = alt.DupTree();
                alt2.DeleteChild(0);
                if (alt2.ChildCount == 0)
                {
                    adaptor.AddChild(alt2, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                }

                alt.SetChild(0, alt.GetChild(0).GetChild(0));
                if (alt.GetChild(0).Type == ANTLRParser.BLOCK && alt.GetChild(0).ChildCount == 1 && alt.GetChild(0).GetChild(0).Type == ANTLRParser.ALT)
                {
                    GrammarAST list = (GrammarAST)adaptor.Nil();
                    foreach (object tree in ((GrammarAST)alt.GetChild(0).GetChild(0)).Children)
                    {
                        adaptor.AddChild(list, tree);
                    }

                    adaptor.ReplaceChildren(alt, 0, 0, list);
                }

                adaptor.AddChild(root, alt);
                adaptor.AddChild(root, alt2);
                return root;
            }
            else if (alt.GetChild(0).Type == ANTLRParser.CLOSURE)
            {
                GrammarAST root = (GrammarAST)adaptor.Nil();

                GrammarAST alt2 = alt.DupTree();
                alt2.DeleteChild(0);
                if (alt2.ChildCount == 0)
                {
                    adaptor.AddChild(alt2, adaptor.Create(ANTLRParser.EPSILON, "EPSILON"));
                }

                PlusBlockAST plusBlockAST = new PlusBlockAST(ANTLRParser.POSITIVE_CLOSURE, adaptor.CreateToken(ANTLRParser.POSITIVE_CLOSURE, "+"), null);
                for (int i = 0; i < alt.GetChild(0).ChildCount; i++)
                {
                    plusBlockAST.AddChild(alt.GetChild(0).GetChild(i));
                }

                alt.SetChild(0, plusBlockAST);

                adaptor.AddChild(root, alt);
                adaptor.AddChild(root, alt2);
                return root;
            }

            return alt;
        }