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 log1p = require( '@stdlib/math/base/special/log1p' );
  var LNHALF = require( '@stdlib/constants/float64/ln-half' );
  
  
  // MAIN //
  
  /**
  * Evaluates the logarithm of the cumulative distribution function (CDF) for a Laplace distribution with location parameter `mu` and scale parameter `b` at value `x`.
  *
  * @param {number} x - input value
  * @param {number} mu - location parameter
  * @param {PositiveNumber} b - scale parameter
  * @returns {number} evaluated logarithm of CDF
  *
  * @example
  * var y = logcdf( 2.0, 0.0, 1.0 );
  * // returns ~-0.07
  *
  * @example
  * var y = logcdf( 5.0, 10.0, 3.0 );
  * // returns ~-2.36
  *
  * @example
  * var y = logcdf( NaN, 0.0, 1.0 );
  * // returns NaN
  *
  * @example
  * var y = logcdf( 2, NaN, 1.0 );
  * // returns NaN
  *
  * @example
  * var y = logcdf( 2.0, 0.0, NaN );
  * // returns NaN
  *
  * @example
  * // Negative scale parameter:
  * var y = logcdf( 2.0, 0.0, -1.0 );
  * // returns NaN
  */
  function logcdf( x, mu, b ) {
  	var z;
  	if (
  		isnan( x ) ||
  		isnan( mu ) ||
  		isnan( b ) ||
  		b <= 0.0
  	) {
  		return NaN;
  	}
  	z = ( x - mu ) / b;
  	if ( x < mu ) {
  		return LNHALF + z;
  	}
  	return LNHALF + log1p( -expm1( -z ) );
  }
  
  
  // EXPORTS //
  
  module.exports = logcdf;
  