+
+/**
+ * @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
+ var result = thenDo(thenDo(thenDo(wrapped_x,
+ zeroOrOnceDo(plusMinus)),d),
+ zeroOrMoreDo(d));
+
+ if (result._tag == "Some"){
+ result.value.matched_type = TokenType.INT;
+ }
+ return result;
+ }
+ let space = (x : MatcheePair) =>{
+ let wrapped_x = toSome(x);
+ let s_aux = orDo(match1Char(' '), match1Char('\t')); // (" " | "\t")
+ var result = thenDo(thenDo(wrapped_x, s_aux), zeroOrMoreDo(s_aux));
+ if (result._tag == "Some"){
+ result.value.matched_type = TokenType.SP;
+ }
+ return result;
+ }
+ let newline = (x : MatcheePair) =>{
+ let wrapped_x = toSome(x);
+ // nl = \r?\n
+ let result = thenDo(thenDo(wrapped_x,
+ zeroOrOnceDo(match1Char('\r'))), match1Char('\n'));
+ if (result._tag == "Some"){
+ result.value.matched_type = TokenType.NL;
+ }
+ return result;
+ }
+
+ let term = (token_list : Array<Token>, x : Some<MatcheePair>)=>{
+ var ln = 1;
+ var col = 0;
+ var old_x = x;
+ let term_list = [newline, space, integer];
+ let term_aux = term_list.reduce((x,y)=> orDo(x,y));
+
+ var new_x : Maybe<MatcheePair> = thenDo(old_x, term_aux);
+ while (new_x._tag != "None"){
+ if (new_x.value.matched_type != TokenType.NL){
+ col += new_x.value.matched.length;
+ token_list.push({text : new_x.value.matched,
+ type: new_x.value.matched_type,
+ ln : ln,
+ col : col});
+
+ }
+ else{
+ col = 0;
+ ln += 1;
+
+ token_list.push({text : new_x.value.matched,
+ type: new_x.value.matched_type,
+ ln : ln,
+ col : col});
+
+ }
+
+
+ old_x = toSome({matched : "",
+ remained : new_x.value.remained});
+ new_x = thenDo(old_x, term_aux);
+ }
+
+ if (old_x.value.remained.length){
+ console.log(token_list);
+ throw new Error("the code can't be tokenized is near Ln. "+ln+", Col."+col
+ +", starting with "+ old_x.value.remained.substring(0,10));
+ }
+
+ return token_list;
+ }
+
+ console.log(term([], input_matchee_pair));
+
+ // TODO: id, string, space, basic operator, 3 marks: @, {, }.
+
+}
+
+