/**
 *  LogarithmPlotter - 2D plotter software to make BODE plots, sequences and distribution functions.
 *  Copyright (C) 2022  Ad5001
 * 
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 * 
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 * 
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

.pragma library

class InputExpression {
    constructor(expression) {
        this.position = 0;
        this.input = expression;
    }
    
    next() {
        return this.input[this.position++];
    }
    
    peek() {
        return this.input[this.position];
    }
    
    skip(char) {
        if(!atEnd() && peek() == char) {
            this.position++;
        } else {
            this.raise("Unexpected character " + peek() + ". Expected character " + char);
        }
    }
    
    atEnd() {
        return this.position >= this.input.length;
    }
    
    raise(message) {
        throw new SyntaxError(message + " at " + this.position + ".")
    }
}