/**
     * Assigns a value to a variable in the current scope.
     * @param {String} vname Variable name
     * @param {%} value Anything
     * @see JXG.JessieCode#sstack
     * @see JXG.JessieCode#scope
     */
    letvar: function (vname, value) {
        if (this.builtIn[vname]) {
            this._warn('"' + vname + '" is a predefined value.');
        }

        this.sstack[this.scope][vname] = value;
    },