Re: two_pi ?

[Sergei Steshenko]

--- On Wed, 8/22/12, Sergei Steshenko <address@hidden> wrote:

> From: Sergei Steshenko <address@hidden>
> Subject: Re: two_pi ?
> To: "Juan Pablo Carbajal" <address@hidden>
> Cc: address@hidden
> Date: Wednesday, August 22, 2012, 3:34 PM
> 
> 
> --- On Wed, 8/22/12, Juan Pablo Carbajal <address@hidden>
> wrote:
> 
> > From: Juan Pablo Carbajal <address@hidden>
> > Subject: Re: two_pi ?
> > To: "Sergei Steshenko" <address@hidden>
> > Cc: address@hidden
> > Date: Wednesday, August 22, 2012, 3:14 PM
> > On Thu, Aug 23, 2012 at 12:09 AM,
> > Juan Pablo Carbajal
> > <address@hidden>
> > wrote:
> > > On Wed, Aug 22, 2012 at 11:58 PM, Sergei
> Steshenko
> > <address@hidden>
> > wrote:
> > >> Hello,
> > >>
> > >> since I' dealing with signals/DSP a lot, and
> since
> > by definition
> > >>
> > >> omega = 2 * pi
> > >>
> > >> , in almost every script of mine I have
> > >>
> > >> two_pi = 2 * pi;
> > >>
> > >> line. And in many functions too, of course.
> > >>
> > >> Is there a built-in two_pi constant ? If not,
> would
> > the developers please introduce it ?
> > >>
> > >> Thanks,
> > >>   Sergei.
> > >>
> _______________________________________________
> > >> Help-octave mailing list
> > >> address@hidden
> > >> https://mailman.cae.wisc.edu/listinfo/help-octave
> > >
> > > haha, there should be one. You are not the first
> > > http://tauday.com/
> > >
> > > hehehe
> > >
> > >
> > > --
> > > M. Sc. Juan Pablo Carbajal
> > > -----
> > > PhD Student
> > > University of Zürich
> > > http://ailab.ifi.uzh.ch/carbajal/
> > 
> > 
> > by that I mean the constant should be tau!!
> > 
> > -- 
> > M. Sc. Juan Pablo Carbajal
> 
> 
> Meanwhile I still need 2 * pi and not 2 / pi, though the
> latter can a be a typo in the article ?
> 
> 'tau' is used in my scripts too, and its meaning is time
> constant, i.e. what is know known in electricity/electronics
> as R * C.
> 
> Thanks,
>   Sergei.
> _______________________________________________
> Help-octave mailing list
> address@hidden
> https://mailman.cae.wisc.edu/listinfo/help-octave
> 

Here's what I have in /usr/include/math.h :

/* Some useful constants.  */
#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

/* The above constants are not adequate for computation using `long double's.
   Therefore we provide as an extension constants with similar names as a
   GNU extension.  Provide enough digits for the 128-bit IEEE quad.  */
#ifdef __USE_GNU
# define M_El           2.7182818284590452353602874713526625L  /* e */
# define M_LOG2El       1.4426950408889634073599246810018921L  /* log_2 e */
# define M_LOG10El      0.4342944819032518276511289189166051L  /* log_10 e */
# define M_LN2l         0.6931471805599453094172321214581766L  /* log_e 2 */
# define M_LN10l        2.3025850929940456840179914546843642L  /* log_e 10 */
# define M_PIl          3.1415926535897932384626433832795029L  /* pi */
# define M_PI_2l        1.5707963267948966192313216916397514L  /* pi/2 */
# define M_PI_4l        0.7853981633974483096156608458198757L  /* pi/4 */
# define M_1_PIl        0.3183098861837906715377675267450287L  /* 1/pi */
# define M_2_PIl        0.6366197723675813430755350534900574L  /* 2/pi */
# define M_2_SQRTPIl    1.1283791670955125738961589031215452L  /* 2/sqrt(pi) */
# define M_SQRT2l       1.4142135623730950488016887242096981L  /* sqrt(2) */
# define M_SQRT1_2l     0.7071067811865475244008443621048490L  /* 1/sqrt(2) */
#endif

- still no two_pi, but there is 2 / pi.

Regards,
  Sergei.