+/**
+ * aux function for midfix operator
+ * @param f function
+ * @param signal the rule name
+ * @returns
+ */
+let midfix = (f, signal) => (x) => {
+ var a = f(x);
+ if (a._tag == "Some") {
+ let ast_tail = slice(a.value.ast, a.value.ast.length - 3);
+ let new_ast = [ast_tail];
+ a.value.ast = new_ast;
+ console.log("+" + signal + "+" + repr(a));
+ }
+ return a;
+};
+let circumfix = (f, signal) => (x) => {
+ var a = f(x);
+ if (a._tag == "Some") {
+ let inner = a.value.ast[a.value.ast.length - 2];
+ console.log("AST====" + repr(a.value.ast));
+ let ast_middle = [inner];
+ let new_ast = [ast_middle];
+ a.value.ast = new_ast;
+ console.log("+" + signal + "+" + repr(a));
+ }
+ return a;
+};
+/** fac1 = "(" expr ")" */
+let fac1 = circumfix((x) => thenDo(thenDo(thenDo(tk.toSome(x), tLParen), expr), tRParen), "fac1");
+let fac2 = tInt;
+let fac = orDo(fac1, fac2);
+/**
+ *
+ * term1 = fac (MUL | DIV) fac
+ */
+let term1 = midfix((x) => thenDo(thenDo(thenDo(tk.toSome(x), fac), orDo(tMul, tDiv)), fac), "term1");
+/**
+ *
+ * term2 = int MUL int
+ */
+let term2 = fac;
+/**
+ * term = term1 | term2
+ */
+let term = orDo(term1, term2);
+/**
+ *
+ * expr1 = term ADD term
+ */
+let expr1 = midfix((x) => thenDo(thenDo(thenDo(tk.toSome(x), term), orDo(tAdd, tSub)), term), "expr1");
+/**
+ * expr2 = term
+ */
+let expr2 = term;
+/**
+ * expr = expr1 | expr2
+ */
+let expr = orDo(expr1, expr2);
+let tokens = tk.tokenize("(4-(3/4))"); //tk.tokenize(argv[2]);
+let tokensFiltered = tokens.filter((x) => {
+ return (x.type != tk.TokenType.NL
+ && x.type != tk.TokenType.SP);
+});
+let wrappedTokens = tk.toSome({
+ matched: [],
+ remained: tokensFiltered,
+ ast: []
+});
+let beta = expr({
+ matched: [],
+ remained: tokensFiltered,
+ ast: []
+});
+console.log(repr(beta));