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/**
* @license Apache-2.0
*
* Copyright (c) 2026 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 bisect = require( './bisect.js' );
 
 
// MAIN //
 
/**
* Evaluates the quantile function for a Wald distribution with mean `mu` and shape parameter `lambda` at a probability `p`.
*
* @param {Probability} p - input value
* @param {PositiveNumber} mu - mean
* @param {NonNegativeNumber} lambda - shape parameter
* @returns {NonNegativeNumber} evaluated quantile function
*
* @example
* var y = quantile( 0.8, 1.0, 1.0 );
* // returns ~1.448
*
* @example
* var y = quantile( 0.5, 4.0, 2.0 );
* // returns ~2.057
*
* @example
* var y = quantile( 1.1, 1.0, 1.0 );
* // returns NaN
*
* @example
* var y = quantile( -0.2, 1.0, 1.0 );
* // returns NaN
*
* @example
* var y = quantile( NaN, 1.0, 1.0 );
* // returns NaN
*
* @example
* var y = quantile( 0.5, NaN, 1.0 );
* // returns NaN
*
* @example
* var y = quantile( 0.5, 1.0, NaN );
* // returns NaN
*
* @example
* // Non-positive mean:
* var y = quantile( 0.5, 0.0, 1.0 );
* // returns NaN
*
* @example
* // Negative shape parameter:
* var y = quantile( 0.5, 1.0, -1.0 );
* // returns NaN
*/
function quantile( p, mu, lambda ) {
	if (
		isnan( p ) ||
		isnan( mu ) ||
		isnan( lambda ) ||
		mu <= 0.0 ||
		lambda < 0.0 ||
		p < 0.0 ||
		p > 1.0
	) {
		return NaN;
	}
	if ( lambda === 0.0 ) {
		return mu;
	}
	return bisect( p, mu, lambda );
}
 
 
// EXPORTS //
 
module.exports = quantile;