man for cmath

[Peng Yu]

Hi,

I need to look up the constants defined in cmath. Although I could
read math.h directly, I'm wondering if there is a man page for it on
linux system?

Thanks,
Peng

 

[Stefan Ram]

I need to look up the constants defined in cmath. Although I could
read math.h directly, I'm wondering if there is a man page for it on
linux system?

Try the function name. For example:

man sin

 

[Matthias Buelow]

man sin

Also helpful is man -k, for example "man -k math". On my installation,
it will show math.h(7posix) which is from the POSIX manpages packages.
However, manpages (and documentation in general) are a sad affair on
Linux, so YMMV.

 

[Peng Yu]

Also helpful is man -k, for example "man -k math". On my installation,
it will show math.h(7posix) which is from the POSIX manpages packages.
However, manpages (and documentation in general) are a sad affair on
Linux, so YMMV.

But neither sin nor "man -k math" would give me the constants, such
as M_PI.

Thanks,
Peng

 

[Stefan Ram]

But neither sin nor "man -k math" would give me the constants,
such as M_PI.

There does not seem to be such an identifier in cmath.

See »7.12 Mathematics <math.h>« in

http://std.dkuug.dk/JTC1/SC22/WG14/www/docs/n843.htm

. To C, pi is 4 * atan(1.0).

 

[Peng Yu]

There does not seem to be such an identifier in cmath.

See »7.12 Mathematics <math.h>« in

http://std.dkuug.dk/JTC1/SC22/WG14/www/docs/n843.htm

. To C, pi is 4 * atan(1.0).

But how come in math.h in the GCC distribution, there are the
following line. You mean these constants are not standard conformable?

#if defined __USE_BSD || defined __USE_XOPEN
# define M_E 2.7182818284590452354 /* e */
# define M_LOG2E 1.4426950408889634074 /* log_2 e */
# define M_LOG10E 0.43429448190325182765 /* log_10 e */
# define M_LN2 0.69314718055994530942 /* log_e 2 */
# define M_LN10 2.30258509299404568402 /* log_e 10 */
# define M_PI 3.14159265358979323846 /* pi */
# define M_PI_2 1.57079632679489661923 /* pi/2 */
# define M_PI_4 0.78539816339744830962 /* pi/4 */
# define M_1_PI 0.31830988618379067154 /* 1/pi */
# define M_2_PI 0.63661977236758134308 /* 2/pi */
# define M_2_SQRTPI 1.12837916709551257390 /* 2/sqrt(pi) */
# define M_SQRT2 1.41421356237309504880 /* sqrt(2) */
# define M_SQRT1_2 0.70710678118654752440 /* 1/sqrt(2) */
#endif


Thanks,
Peng