std::log10,std::log10f,std::log10l (3) - Linux Manuals

std::log10,std::log10f,std::log10l: std::log10,std::log10f,std::log10l

NAME

std::log10,std::log10f,std::log10l - std::log10,std::log10f,std::log10l

Synopsis

Defined in header <cmath>
float log10 ( float arg );
float log10f( float arg ); (since C++11)
double log10 ( double arg ); (1) (2)
long double log10 ( long double arg );
long double log10l( long double arg ); (3) (since C++11)
double log10 ( IntegralType arg ); (4) (since C++11)

1-3) Computes the common (base-10) logarithm of arg.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to 2) (the argument is cast to double).

Parameters

arg - value of floating-point or Integral_type

Return value

If no errors occur, the common (base-10) logarithm of arg (log
10(arg) or lg(arg)) is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported)
If a pole error occurs, -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL is returned.

Error handling

Errors are reported as specified in math_errhandling.
Domain error occurs if arg is less than zero.
Pole error may occur if arg is zero.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),

* If the argument is ±0, -∞ is returned and FE_DIVBYZERO is raised.
* If the argument is 1, +0 is returned
* If the argument is negative, NaN is returned and FE_INVALID is raised.
* If the argument is +∞, +∞ is returned
* If the argument is NaN, NaN is returned

Example

// Run this code

  #include <iostream>
  #include <cmath>
  #include <cerrno>
  #include <cstring>
  #include <cfenv>
  #pragma STDC FENV_ACCESS ON
  int main()
  {
      std::cout << "log10(1000) = " << std::log10(1000) << '\n'
                << "log10(0.001) = " << std::log10(0.001) << '\n'
                << "base-5 logarithm of 125 = " << std::log10(125)/std::log10(5) << '\n';
      // special values
      std::cout << "log10(1) = " << std::log10(1) << '\n'
                << "log10(+Inf) = " << std::log10(INFINITY) << '\n';
      // error handling
      errno = 0;
      std::feclearexcept(FE_ALL_EXCEPT);
      std::cout << "log10(0) = " << std::log10(0) << '\n';
      if (errno == ERANGE)
          std::cout << " errno == ERANGE: " << std::strerror(errno) << '\n';
      if (std::fetestexcept(FE_DIVBYZERO))
          std::cout << " FE_DIVBYZERO raised\n";
  }

Possible output:

  log10(1000) = 3
  log10(0.001) = -3
  base-5 logarithm of 125 = 3
  log10(1) = 0
  log10(+Inf) = inf
  log10(0) = -inf
      errno == ERANGE: Numerical result out of range
      FE_DIVBYZERO raised