old_contents: 'use strict';
  
  // MODULES //
  
  var isObject = require( 'validate.io-object' );
  var isNumber = require( 'validate.io-number-primitive' );
  var isPositiveInteger = require( 'validate.io-positive-integer' );
  
  
  // VALIDATE //
  
  /**
  * FUNCTION: validate( opts, options )
  *	Validates function options.
  *
  * @param {Object} opts - destination for validated options
  * @param {Object} options - function options
  * @param {Number} [options.max_terms] - maximum number of terms
  * @param {Number} [options.tolerance] - further terms are only added as long as the next term is greater than current term times the tolerance
  * @param {Number} [options.init] - whether to keep the leading b term
  * @returns {Null|Error} null or an error
  */
  function validate( opts, options ) {
  	if ( !isObject( options ) ) {
  		return new TypeError( 'invalid input argument. Options argument must be an object. Value: `' + options + '`.' );
  	}
  	if ( options.hasOwnProperty( 'max_terms' ) ) {
  		opts.max_terms = options.max_terms;
  		if ( !isPositiveInteger( opts.max_terms ) ) {
  			return new TypeError( 'invalid option. Maximum iterations option must be an integer. Option: `' + opts.max_terms + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'tolerance' ) ) {
  		opts.tolerance = options.tolerance;
  		if ( !isNumber( opts.tolerance ) ) {
  			return new TypeError( 'invalid option. Tolerance option must be a number primitive. Option: `' + opts.tolerance + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'init' ) ) {
  		opts.init = options.init;
  		if ( !isNumber( opts.init ) ) {
  			return new TypeError( 'invalid option. Initial value option must be a number primitive. Option: `' + opts.init + '`.' );
  		}
  	}
  	return null;
  } // end FUNCTION validate()
  
  
  // EXPORTS //
  
  module.exports = validate;
  
new_contents: 'use strict';
  
  // MODULES //
  
  var isObject = require( 'validate.io-object' );
  var isNumber = require( 'validate.io-number-primitive' );
  var isPositiveInteger = require( 'validate.io-positive-integer' );
  
  
  // VALIDATE //
  
  /**
  * FUNCTION: validate( opts, options )
  *	Validates function options.
  *
  * @param {Object} opts - destination for validated options
  * @param {Object} options - function options
  * @param {Number} [options.max_terms] - maximum number of terms
  * @param {Number} [options.tolerance] - further terms are only added as long as the next term is greater than current term times the tolerance
  * @param {Number} [options.init] - initial value of the resulting sum
  * @returns {Null|Error} null or an error
  */
  function validate( opts, options ) {
  	if ( !isObject( options ) ) {
  		return new TypeError( 'invalid input argument. Options argument must be an object. Value: `' + options + '`.' );
  	}
  	if ( options.hasOwnProperty( 'max_terms' ) ) {
  		opts.max_terms = options.max_terms;
  		if ( !isPositiveInteger( opts.max_terms ) ) {
  			return new TypeError( 'invalid option. Maximum iterations option must be an integer. Option: `' + opts.max_terms + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'tolerance' ) ) {
  		opts.tolerance = options.tolerance;
  		if ( !isNumber( opts.tolerance ) ) {
  			return new TypeError( 'invalid option. Tolerance option must be a number primitive. Option: `' + opts.tolerance + '`.' );
  		}
  	}
  	if ( options.hasOwnProperty( 'init' ) ) {
  		opts.init = options.init;
  		if ( !isNumber( opts.init ) ) {
  			return new TypeError( 'invalid option. Initial value option must be a number primitive. Option: `' + opts.init + '`.' );
  		}
  	}
  	return null;
  } // end FUNCTION validate()
  
  
  // EXPORTS //
  
  module.exports = validate;
  
subject: Fix parameter description