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 isnan = require( '@stdlib/math-base-assert-is-nan' );
  var expm1 = require( '@stdlib/math-base-special-expm1' );
  var pow = require( '@stdlib/math-base-special-pow' );
  
  
  // MAIN //
  
  /**
  * Evaluates the cumulative distribution function (CDF) for a Weibull distribution with scale parameter `k` and shape parameter `lambda` at a value `x`.
  *
  * @param {number} x - input value
  * @param {PositiveNumber} k - scale parameter
  * @param {PositiveNumber} lambda - shape parameter
  * @returns {Probability} evaluated CDF
  *
  * @example
  * var y = cdf( 2.0, 1.0, 1.0 );
  * // returns ~0.865
  *
  * @example
  * var y = cdf( -1.0, 2.0, 2.0 );
  * // returns 0.0
  *
  * @example
  * var y = cdf( +Infinity, 4.0, 2.0 );
  * // returns 1.0
  *
  * @example
  * var y = cdf( -Infinity, 4.0, 2.0 );
  * // returns 0.0
  *
  * @example
  * var y = cdf( NaN, 0.0, 1.0 );
  * // returns NaN
  *
  * @example
  * var y = cdf( 0.0, NaN, 1.0 );
  * // returns NaN
  *
  * @example
  * var y = cdf( 0.0, 0.0, NaN );
  * // returns NaN
  *
  * @example
  * var y = cdf( 2.0, 0.0, -1.0 );
  * // returns NaN
  */
  function cdf( x, k, lambda ) {
  	if (
  		isnan( x ) ||
  		isnan( k ) ||
  		isnan( lambda ) ||
  		k <= 0.0 ||
  		lambda <= 0.0
  	) {
  		return NaN;
  	}
  	if ( x < 0.0 ) {
  		return 0.0;
  	}
  	return -expm1( -pow( x / lambda, k ) );
  }
  
  
  // EXPORTS //
  
  module.exports = cdf;
  