TOMS179 is a C library which implements ACM TOMS algorithm 179, for evaluating the modified Beta function.
While 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, many of the early algorithms are not available. This is one of them. I typed it in.
The original algorithm was published in the Algol language. Shortly therafter, a distinct FORTRAN77 algorithm was published as a "remark" to the original algorithm. A few modifications to the FORTRAN77 program were proposed in a subsequent "remark".
prob = mdbeta ( x, p, q, &ier )where
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
TOMS179 is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version and a Python version.
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You can go up one level to the C source codes.