@oat-sa/tao-item-runner-qti/src/scoring/processor/expressions/operators/lcm.js

TAO QTI Item Runner modules

/*
 * 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; under version 2
 * of the License (non-upgradable).
 *
 * 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright (c) 2015-2019 (original work) Open Assessment Technlogies SA (under the project TAO-PRODUCT);
 *
 */
/**
 * The lcm operator processor.
 * @see http://www.imsglobal.org/question/qtiv2p1/imsqti_infov2p1.html#element106213
 *
 * @author Bertrand Chevrier <bertrand@taotesting.com>
 */
import _ from 'lodash';

var lcmProcessor = {

    constraints: {
        minOperand: 1,
        lcmOperand: -1,
        cardinality: ['single', 'multiple', 'ordered'],
        baseType: ['integer']
    },

    operands: [],

    /**
     * Process operands and returns the lcm.
     * @type {OperatorProcessor}
     * @exports taoQtiItem/scoring/processor/expressions/operators/lcm
     */
    process: function() {

        var result = {
            cardinality: 'single',
            baseType: 'integer'
        };
        var castedOperands;

        //if at least one operand is null or infinity, then break and return null
        if (_.some(this.operands, _.isNull) === true) {
            return null;
        }

        castedOperands = this.preProcessor.parseOperands(this.operands);

        //if at least one operand is a not a number,  then break and return null
        if (!castedOperands.every(this.preProcessor.isNumber)) {
            return null;
        }

        if (castedOperands.value().indexOf(0) !== -1) {
            result.value = 0;
            return result;
        }

        result.value = lcm(castedOperands.value());

        return result;
    }
};

/**
 * Calculates least common multiple for two ore more integers
 * @param {Array<number|Number>}numbers
 * @returns {number} least common multiple
 */
function lcm(numbers) {
    var n = numbers.length,
        a = Math.abs(numbers[0]),
        b,
        c,
        i;

    for (i = 1; i < n; i++) {
        b = Math.abs(numbers[i]);
        c = a;
        while (a && b) {
            a > b ? a %= b : b %= a;
        }
        a = Math.abs(c * numbers[i]) / (a + b);
    }
    return a;
}

export default lcmProcessor;