man for cmath

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  • Peng Yu
    #1

    man for cmath

    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
    Tags: None
    • Matthias Buelow
      #2
      Re: man for cmath

      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.

        Comment

        • Peng Yu
          #3
          Re: man for cmath

          On Jul 14, 8:29 am, Matthias Buelow <m...@incubus.d ewrote:
          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.
          But neither sin nor "man -k math" would give me the constants, such
          as M_PI.

          Thanks,
          Peng

            Comment

            • Peng Yu
              #4
              Re: man for cmath

              On Jul 14, 12:39 pm, r...@zedat.fu-berlin.de (Stefan Ram) wrote:
              Peng Yu <PengYu...@gmai l.comwrites:
              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).
              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 2.7182818284590 452354 /* e */
              # define M_LOG2E 1.4426950408889 634074 /* log_2 e */
              # define M_LOG10E 0.4342944819032 5182765 /* log_10 e */
              # define M_LN2 0.6931471805599 4530942 /* log_e 2 */
              # define M_LN10 2.3025850929940 4568402 /* log_e 10 */
              # define M_PI 3.1415926535897 9323846 /* pi */
              # define M_PI_2 1.5707963267948 9661923 /* pi/2 */
              # define M_PI_4 0.7853981633974 4830962 /* pi/4 */
              # define M_1_PI 0.3183098861837 9067154 /* 1/pi */
              # define M_2_PI 0.6366197723675 8134308 /* 2/pi */
              # define M_2_SQRTPI 1.1283791670955 1257390 /* 2/sqrt(pi) */
              # define M_SQRT2 1.4142135623730 9504880 /* sqrt(2) */
              # define M_SQRT1_2 0.7071067811865 4752440 /* 1/sqrt(2) */
              #endif


              Thanks,
              Peng

                Comment

                • Paavo Helde
                  #5
                  Re: man for cmath

                  Peng Yu <PengYu.UT@gmai l.comkirjutas:
                  On Jul 14, 12:39 pm, r...@zedat.fu-berlin.de (Stefan Ram) wrote:
                  >Peng Yu <PengYu...@gmai l.comwrites:
                  >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).
                  >
                  But how come in math.h in the GCC distribution, there are the
                  following line. You mean these constants are not standard conformable?
                  After 3 minutes of Google search:

                  http://www.network-theory.co.uk/docs...cintro_27.html :

                  "The constant M_PI is not part of the ANSI/ISO C standard library (it
                  comes from the BSD version of Unix)."

                  hth
                  Paavo

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