@masala/parser/src/lib/stream/stream.js

Masala Parser

/*
 * Parsec
 * https://github.com/d-plaindoux/parsec
 *
 * Copyright (c) 2016 Didier Plaindoux
 * Licensed under the LGPL2 license.
 */

import atry from '../data/try';

/**
 * Abstract methods:
 * - unsafeGet(index)
 */
class Stream {
    constructor() {}

    // Stream 'a => number -> number
    location(index) {
        return index;
    }

    // Stream 'a => number -> Try 'a
    get(index) {
        try {
            if (this.endOfStream(index)) {
                return atry.failure(new Error('End of stream reached'));
            } else {
                return atry.success(this.unsafeGet(index));
            }
        } catch (e) {
            return atry.failure(e);
        }
    }

    // Stream 'a => [Comparable 'a] -> number -> boolean
    subStreamAt(s, index) {
        for (var i = 0; i < s.length; i++) {
            var value = this.get(i + index);
            if (!value.isSuccess() || value.success() !== s[i]) {
                return false;
            }
        }

        return true;
    }
}

export default Stream;