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/**
* @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 rateval = require( './rational_pq.js' );
// VARIABLES //
var root1 = 1569415565.0 / 1073741824.0;
var root2 = ( 381566830.0 / 1073741824.0 ) / 1073741824.0;
var root3 = 0.9016312093258695918615325266959189453125e-19;
var Y = 0.99558162689208984;
// MAIN //
/**
* Evaluates the digamma function over interval `[1,2]`.
*
* @private
* @param {number} x - input value
* @returns {number} function value
*/
function digamma( x ) {
var g;
var r;
g = x - root1;
g -= root2;
g -= root3;
r = rateval( x-1.0 );
return (g*Y) + (g*r);
}
// EXPORTS //
module.exports = digamma;
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