jaycc/rex.js

### the Javascript C Compiler

// Regular EXception
let QM;
let Star;
let $;
let $$;
QM = Symbol();
Star = Symbol();
$ = Symbol();
$$ = Symbol();
export { QM, Star, $, $$ };
let wildcard;
wildcard = (x) => ((x == QM)
    || (x == Star)
    || (x == $)
    || (x == $$));
export class REX {
    es;
    caps;
    capidx;
    capturing;
    equality;
    constructor(input, eq) {
        // add sanity checks
        this.es = input;
        this.caps = [];
        this.capidx = null;
        this.capturing = false;
        this.equality = eq;
    }
    match(xs) {
        return this.match_(xs, []);
    }
    match_(xs, cap_) {
        let x;
        let e;
        let cap;
        cap = cap_;
        // console.log('-- xs=', xs);
        // console.log('-- cap=', cap);
        x = xs.shift()
            || null;
        e = this.es.shift()
            || null;
        if (!x)
            if (!this.es.length)
                return true;
            else
                return false;
        else if (!e)
            return false;
        if ((this.capidx !== null) && (this.capturing)) {
            // console.log('  * adding cap ', x, 'e=', e, 'x=', x);
            cap = cap.concat([x]);
        }
        if (!wildcard(e)) {
            if (this.equality(e, x))
                return this.match_(xs, cap);
            else
                return false;
        }
        else {
            switch (e) {
                case QM:
                    // console.log('[?]');
                    return this.match_(xs, cap);
                    break;
                case Star:
                    // console.log('[*]');
                    if ((this.es[0] == x))
                        void 0;
                    else if ((wildcard(this.es[0])
                        && (this.equality(this.es[1], x)))) {
                        if (this.es[0] == $$) {
                            cap.pop();
                            if (this.capidx === null)
                                throw "Syntax error";
                            this.caps[this.capidx] = cap;
                            this.capturing = false;
                            this.es.shift();
                            return this.match_(xs, []);
                        }
                        this.es.shift() &&
                            this.match_(xs, cap);
                    }
                    else
                        this.es = [e].concat(this.es);
                    return this.match_(xs, cap);
                    break;
                case $:
                    // console.log('[$]');
                    if (this.capidx === null)
                        this.capidx = 0;
                    else
                        this.capidx++;
                    this.capturing = true;
                    return this.match_([x].concat(xs), []);
                    break;
                case $$:
                    console.log('[$$]');
                    if (this.capidx === null)
                        throw "Syntax error";
                    cap.pop();
                    this.caps[this.capidx] = cap;
                    this.capturing = false;
                    // console.log('  cap=', cap);
                    return this.match_([x].concat(xs), []);
                    break;
            }
        }
        return false;
    }
}