TOMS443
Evaluation of Lambert's W function.
TOMS443
is a FORTRAN90 library which
evaluates Lambert's W function.
This is a version of ACM TOMS algorithm 443,
by Fritsch, Shafer and Crowley.
Lambert's W function W(X) satisfies the equation
W(x) * exp ( W(x) ) = x
The text of many ACM TOMS algorithms is available online
through ACM:
http://www.acm.org/pubs/calgo
or NETLIB:
http://www.netlib.org/toms/index.html.
Usage:

w = wew ( x, en )

where X, is the argument, EN is the last correction
to the output value made by the Newton iteration, and the value
of W(X)) is returned in WEW.
Languages:
TOMS443 is available in
a C version and
a C++ version and
a FORTRAN77 version and
a FORTRAN90 version and
a MATLAB version.
Related Data and Programs:
TEST_VALUES,
a FORTRAN90 library which
contains routines which return sample values of various functions,
including the modified beta function, and the logarithm of the
gamma function.
TOMS743,
a FORTRAN90 library which
evaluates Lambert's W function.
This is a version of ACM TOMS algorithm 743,
by Barry, Barry and CulliganHensley.
Reference:

Fred Fritsch, RE Shafer, WP Crowley,
Algorithm 443:
Solution of the Transcendental Equation W*exp(W)=X,
Communications of the ACM,
Volume 16, Number 1, February 1973, pages 123124.

Andrew Barry, S. J. Barry, Patricia CulliganHensley,
Algorithm 743: WAPR  A Fortran routine for calculating real
values of the Wfunction,
ACM Transactions on Mathematical Software,
Volume 21, Number 2, June 1995, pages 172181.
Source Code:
Examples and Tests:
List of Routines:

WEW_A evaluates Lambert's W function using
code appropriate for a CDC 6600 (default 64 bit precision).

WEW_B evaluates Lambert's W function using
code appropriate for a computer with precision of
about 3.0E07.
You can go up one level to
the FORTRAN90 source codes.
Last revised on 08 June 2014.