J3/05-132r2
To: J3
From: Dan Nagle
Subject: libm math functions
Date: 2005 Feb 09
Most Fortran vendors also support C/C++ compilers,
or utilize C/C++ RTLs to supply low-level services.
The C/C++ libm contains a few mathematical routines
which would be of use to Fortran programs. Standardizing
names for these routines aids portability
of Fortran programs.
This is J3/04-246 at M167, where the Hate .. Love vote was 0 - 3 - 6 - 0
Number:
Title: C libm functions as Fortran intrinsics
Submitted By: J3
Status: For Consideration
References: C99 7.12 Mathematics page 211 et seq.
Unix Programmer's Manual, Volume 2, System calls
and Library Routines (3m)
Basic Functionality: Add the Bessel functions, hypot, and error functions
to the Fortran intrinsic function set
for real arguments.
Rationale: Fortran is mainly used for numerical problems, supplying
mathematical functions of proven utility will assist
Fortran is continuing as the premier mathematical programming
language in the world today.
Estimated Impact: The estimated impact at 167 was 4 on the John Reid scale.
These are proposed intrinsic functions, no other feature
is affected. Impact on vendors is minimal,
as most vendors support these functions anyway
for their C/C++ compilers.
Detailed Specification: Add subsections to Section 13 detailing
the Fortran names for these procedures. (The C names
should not be used due to the common usage, in
Fortran, of names such as j0 etc.)
The functions are (the C names):
Bessel functions (j0, j1, jn, y0, y1, yn)
Error Functions (erf, erfc)
Hypotenuse (hypot)
Gamma and log gamma (tgamma, lgamma)
The detailed mathematical specification of these
procedures is given in the references above.
The intention is to allow the vendor to use
the procedure supplied by libm, so the exact
specification is left to libm, which is most likely
what the applications programmer wants.
Since Fortran does not support the concept
of external variables, the signgam variable of lgamma
may be defined as an optional intent(out)
argument.
Edits would include adding to the list in 13.5.2:
BESSEL_J0
BESSEL_J1
BESSEL_JN
BESSEL_Y0
BESSEL_Y1
BESSEL_YN
COMP_ERROR_FUNC
ERROR_FUNC
GAMMA_FUNC
HYPOT
LOG_GAMMA_FUNC
History: J3/04-246 at M167, J3/05-132 at M171