Method validate

docs/tests/v3/es6/js/sanddance-test-es6.js:17275–17279

()

        return this;
    }
    validate() {
        let valid = this.length === this.ELEMENTS;
        for(let i = 0; i < this.ELEMENTS; ++i)valid = valid && Number.isFinite(this[i]);
        return valid;
    }
    sub(a) {
        return this.subtract(a);
    }