function command( pres ) {
	return onCommand;

	/**
	* Returns the current presentation slide index.
	*
	* ## Notes
	*
	* -   The returned index is the nominal (i.e., one-based) slide index.
	*
	* @private
	* @returns {integer} current presentation slide index
	*/
	function onCommand() {
		return pres.currentSlide;
	}
}
Returns a callback to be invoked upon calling the `currentSlide` command.

@private
@param {Presentation} pres - presentation instance
@returns {Function} callback