+
+/**
+ * @description "or", like the regex `( f1 | f2 )` .
+ * It returns a function `f` of which the argument is`x`.
+ * if `f1(x)` is None, then `f` returns `f2(x)`. Otherwise,
+ * `F` returns `f1(x)`.
+ * @param f1 : 1st function to be compared
+ * @param f2 : 2nd function to be compared
+ * @returns:the combined function
+ */
+export function orDo<T>(f1 : Function, f2: Function) : (x : T ) => Maybe<T>{
+ return (x) => {
+ let f1x : Maybe<T> = (f1(x));
+ {
+ if (f1x._tag == "None"){
+ return f2(x);
+ }
+ else{
+ return f1x;
+ }
+ }
+ };
+}
+
+
+/**
+* @description repeating matching function `f`
+* zero or more times, like the asterisk `*` in regex `f*` .
+* @param f : the function to be repeated 0+ times.
+* @returns:the combined function
+*/
+export function zeroOrMoreDo<T>(f : Function): (x : T) => Maybe<T>{
+ return (x)=>{
+ var wrapped_old_x : Maybe<T> = {_tag: "Some", value : x};
+ var wrapped_new_x : Maybe<T> = wrapped_old_x;
+
+ while (wrapped_new_x._tag != "None"){
+ wrapped_old_x = wrapped_new_x;
+ wrapped_new_x = thenDo(wrapped_old_x, f);
+ };
+
+ return wrapped_old_x;
+ };
+}
+
+/**
+* @description Not. like the `^` inside regex of [^f].
+* returns a function `F(x)` such that if `f(x)` is `None`,
+* returns the x consuming a char; if `f(x)` is not None, F(x)
+* returns `None`.
+* @param f: the function forbidden to be matched.
+* @returns: combined function `F`.
+*/
+export function notDo<T>(f : Function): (x : T) => Maybe<T>{
+ return (x)=>{
+ let wrapped_x : Maybe<T> = {
+ _tag : "Some",
+ value : x
+ };
+ let f_x = thenDo(wrapped_x, f);
+
+ if (f_x._tag != "None"){
+ return {_tag:"None"};
+ }else{
+ return thenDo(wrapped_x, matchAny);
+ }
+ };
+}
+
+/**
+ * if `x` is matched by `f` once, returns `f(x)`. Otherwise,
+ * returns x
+ * similar to `?` in regex `f?`.
+ * @param f : the function to be matched
+ * @returns return wrapped f(x)
+ */
+export function zeroOrOnceDo<T>(f : Function): (x : T) => Maybe<T>{
+ return (x)=>{
+ var wrapped_old_x : Maybe<T> = {_tag: "Some", value : x};
+ var wrapped_new_x = thenDo(wrapped_old_x, f);
+
+ if (wrapped_new_x._tag != "None"){
+ return wrapped_new_x;
+ }else{
+ return wrapped_old_x;
+ }
+ };
+}
+
+
+export function tokenize(input : string){
+ var input_matchee_pair : Maybe<MatcheePair> = toSome(
+ {matched:"",
+ remained: input});
+
+ // integer = ([+]|[-])\d\d?
+ let integer = (x : MatcheePair) =>
+ { let wrapped_x = toSome(x);
+ let plusMinus = orDo(match1Char('+'), match1Char('-')); // ([+]|[-])
+ let d = matchRange('0','9'); // \d
+ return thenDo(thenDo(thenDo(wrapped_x,
+ zeroOrOnceDo(plusMinus)),d),
+ zeroOrMoreDo(d));
+ }
+ console.log(input+", result: ");
+ console.log(thenDo(input_matchee_pair, integer));
+ // TODO: id, string, space, basic operator, 3 marks: @, {, }.
+
+}
+
+tokenize("+123");
+tokenize("123");
+tokenize("-123");
+tokenize(" 123");
+tokenize("c123");
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