parjs/internal/combinators/backtrack.js

A parser-combinator library for JavaScript.

"use strict";
/**
 * @module parjs/combinators
 */
/** */
Object.defineProperty(exports, "__esModule", { value: true });
const parser_1 = require("../parser");
const combinator_1 = require("./combinator");
/**
 * Applies the source parser. If it succeeds, backtracks to the current position in the input
 * and yields the result.
 */
function backtrack() {
    return combinator_1.defineCombinator(source => {
        return new class Backtrack extends parser_1.ParjserBase {
            constructor() {
                super(...arguments);
                this.type = "backtrack";
                this.expecting = source.expecting;
            }
            _apply(ps) {
                let { position } = ps;
                source.apply(ps);
                if (ps.isOk) {
                    // if inner succeeded, we backtrack.
                    ps.position = position;
                }
                // whatever code ps had, we return it.
            }
        }();
    });
}
exports.backtrack = backtrack;

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