+/**
+ *
+ * @param m : the `TokenPair` to be consumed.
+ * @returns if the length of `m.remained` >= 1; consumes the matchee by 1 token
+ * and wraps it in `Some`,
+ * otherwise, returns `None`.
+ */
+export function matchAny(m: TokenPair): Maybe<TokenPair> {
+ if (m.remained.length >= 1) {
+ return {
+ _tag: "Some", value: {
+ matched: m.matched.concat(m.remained[0]),
+ remained: m.remained.slice(1),
+ ast : [m.remained[0]],
+ }
+ };
+ } else {
+ return { _tag: "None" };
+ }
+}
+
+/**
+ * like `f1 | f2` in regex
+ * @param f1 the first tried function
+ * @param f2 the second tried function
+ * @returns wrapped result
+ */
+function orDo(f1 : Function, f2 : Function){
+ return (x : TokenPair) =>{
+ let res1 : Maybe<TokenPair> = f1(x);
+ if (res1._tag == "Some"){
+ return res1;
+ }else{
+ let res2 : Maybe<TokenPair> = f2(x);
+ return res2;
+ }
+ }
+}
+
+/**
+ * like regex [^c]
+ * @param f input token function. one token only.
+ * @returns combined finction
+ */
+function notDo(f : Function){
+ return (x : TokenPair) =>{
+ let res1 : Maybe<TokenPair> = f(x);
+ if (res1._tag == "Some"){
+ return {_tag:"None"};
+ }else{
+ let res2 = matchAny(x);
+ return res2;
+ }
+ }
+}
+
+function matchToken(typeName : string, value? : string):
+ (t : TokenPair) => Maybe<TokenPair>{
+ return (t)=>{
+ let headToken = t.remained[0];
+ if (headToken.type != typeName){
+ return {_tag:"None"};
+ }else{
+ if (value === undefined || value == headToken.value){
+ let newTokenPair = {
+ matched: t.matched.concat(headToken),
+ remained: t.remained.slice(1),
+ ast : [headToken]
+ };
+ return {_tag : "Some", value : newTokenPair};
+ }else{
+ return {_tag:"None"};
+ }
+ };
+ }
+};