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- /*
- Implementation of the Fukushima method for the Lambert W function
-
- Copyright (C) 2015 Darko Veberic, darko.veberic@ijs.si
-
- This program is free software: you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation, either version 3 of the License, or
- (at your option) any later version.
-
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-
- /*
- This code is based on the following publication and its author's fortran code:
- Toshio Fukushima, "Precise and fast computation of Lambert W-functions without
- transcendental function evaluations", J. Comp. Appl. Math. 244 (2013) 77-89.
- */
-
- #ifndef _FukushimaLambertW_h_
- #define _FukushimaLambertW_h_
-
- #include <limits>
-
-
- namespace Fukushima {
-
- double LambertW0(const double x);
-
- double LambertWm1(const double x);
-
-
- inline
- double
- LambertW(const int branch, const double x)
- {
- switch (branch) {
- case -1: return LambertWm1(x);
- case 0: return LambertW0(x);
- default: return std::numeric_limits<double>::quiet_NaN();
- }
- }
-
- }
-
-
- #endif
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