newlib/libm/complex/clog10.c

   1 /*
   2 FUNCTION
   3         <<clog10>>, <<clog10f>>---complex base-10 logarithm
   4
   5 INDEX
   6         clog10
   7 INDEX
   8         clog10f
   9
  10 SYNOPSIS
  11        #define _GNU_SOURCE
  12        #include <complex.h>
  13        double complex clog10(double complex <[z]>);
  14        float complex clog10f(float complex <[z]>);
  15
  16
  17 DESCRIPTION
  18         These functions compute the complex base-10 logarithm of <[z]>.
  19         <<clog10>> is equivalent to <<clog>>(<[z]>)/<<log>>(10).
  20
  21         <<clog10f>> is identical to <<clog10>>, except that it performs
  22         its calculations on <<floats complex>>.
  23
  24 RETURNS
  25         The clog10 functions return the complex base-10 logarithm value.
  26
  27 PORTABILITY
  28         <<clog10>> and <<clog10f>> are GNU extensions.
  29
  30 */
  31
  32 #include <complex.h>
  33 #include <math.h>
  34
  35 double complex
  36 clog10(double complex z)
  37 {
  38         double complex w;
  39         double p, rr;
  40
  41         rr = cabs(z);
  42         p = log10(rr);
  43         rr = atan2(cimag(z), creal(z)) * M_IVLN10;
  44         w = p + rr * I;
  45         return w;
  46 }