| LOG(3) | Library Functions Manual | LOG(3) | 
log, logf,
  log10, log10f,
  log1p, log1pf,
  log2, log2f —
#include <math.h>
double
  
  log(double
    x);
float
  
  logf(float
    x);
double
  
  log10(double
    x);
float
  
  log10f(float
    x);
double
  
  log1p(double
    x);
float
  
  log1pf(float
    x);
double
  
  log2(double
    x);
float
  
  log2f(float
    x);
log() and logf()
      functions return the natural logarithm.log10() and log10f()
      functions return the base 10 logarithm.log1p() and log1pf()
      functions return the natural logarithm of (1.0 + x)
      accurately even for very small values of x.log2() and log2f()
      functions return the base 2 logarithm.log(), log10(), and
      log2() families return either
      -HUGE_VAL, -HUGE_VALF, or
      -HUGE_VALL, whereas the
      log1p() family returns
    x.log(),
      log10(), and log2()
      families return +0.0. If x is -1.0, the
      log1p() family returns
      -HUGE_VAL, -HUGE_VALF, or
      -HUGE_VALL.In addition, on a VAX, errno is set to
    EDOM and the reserved operand is returned by
    log() unless x > 0, by
    log1p() unless x > -1.
log() function appeared in
  Version 1 AT&T UNIX.
| September 2, 2019 | NetBSD 10.0 |