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TOMS743\ Evaluation of Lambert’s W function. {#toms743-evaluation-of-lamberts-w-function. align=”center”} ===================================

TOMS743 is a C++ library which evaluates Lambert’s W function. This is a version of ACM TOMS algorithm 743, by Barry, Barry and Culligan-Hensley.

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.md.

Licensing: {#licensing align=”center”}

The computer code and data files made available on this web page are distributed under the GNU LGPL license.

Languages: {#languages align=”center”}

TOMS743 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: {#related-data-and-programs align=”center”}

TEST_VALUES, a C++ library which contains routines which return sample values of various functions, including the modified beta function, and the logarithm of the gamma function.

TOMS443, a C++ library which evaluates Lambert’s W function. This is a version of ACM TOMS algorithm 443.

Reference: {#reference align=”center”}

1. 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 123-124.
2. Andrew Barry, S. J. Barry, Patricia Culligan-Hensley,\ Algorithm 743: WAPR - A Fortran routine for calculating real values of the W-function,\ ACM Transactions on Mathematical Software,\ Volume 21, Number 2, June 1995, pages 172-181.

Source Code: {#source-code align=”center”}

• toms743.cpp, the source code.
• toms743.hpp, the source code.

Examples and Tests: {#examples-and-tests align=”center”}

• toms743_prb.cpp, a sample calling program.
• toms743_prb_output.txt, the output file.

List of Routines: {#list-of-routines align=”center”}

• BISECT approximates the W function using bisection.
• CRUDE returns a crude approximation for the W function.
• NBITS_COMPUTE computes the mantissa length minus one.
• TIMESTAMP prints out the current YMDHMS date as a timestamp.
• WAPR approximates the W function.

You can go up one level to the C++ source codes.

Last revised on 17 June 2014.