text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2018 The Stdlib Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  'use strict';
  
  // MODULES //
  
  var isDateObject = require( '@stdlib/assert-is-date-object' );
  var isInteger = require( '@stdlib/assert-is-integer' ).isPrimitive;
  var floor = require( '@stdlib/math-base-special-floor' );
  
  
  // VARIABLES //
  
  var SHORT_YEAR = 52;
  var LONG_YEAR = 53;
  
  
  // FUNCTIONS //
  
  /**
  * Formula for determining if a year is "long" or "short".
  *
  * @private
  * @param {integer} yr - year
  * @returns {integer} result
  */
  function p( yr ) {
  	var v = yr + floor( yr/4 ) - floor( yr/100 ) + floor( yr/400 );
  	return v % 7;
  }
  
  
  // MAIN //
  
  /**
  * Returns the number of ISO weeks in a year.
  *
  * @param {(integer|Date)} value - year or `Date` object
  * @throws {TypeError} must provide either an integer or a `Date` object
  * @returns {integer} number of ISO weeks in a year
  *
  * @example
  * var num = isoWeeksInYear();
  * // returns <number>
  *
  * @example
  * var num = isoWeeksInYear( 2015 );
  * // returns 53
  *
  * @example
  * var num = isoWeeksInYear( 2017 );
  * // returns 52
  */
  function isoWeeksInYear( value ) {
  	var yr;
  	if ( arguments.length ) {
  		if ( isDateObject( value ) ) {
  			yr = value.getFullYear();
  		} else if ( isInteger( value ) ) {
  			yr = value;
  		} else {
  			throw new TypeError( 'invalid argument. Must provide either an integer or a `Date` object. Value: `'+value+'`.' );
  		}
  	} else {
  		// Note: cannot cache as application could cross over into a new year:
  		yr = ( new Date() ).getFullYear();
  	}
  	if ( p( yr ) === 4 || p( yr-1 ) === 3 ) {
  		return LONG_YEAR;
  	}
  	return SHORT_YEAR;
  }
  
  
  // EXPORTS //
  
  module.exports = isoWeeksInYear;
  