C++ Standard Library C++ STL Library

C++ <complex> - log() Function

The C++ <complex> log() function returns natural logarithm (base-e) of a complex number z. It is a function on complex plane, and has a branch cut, from 0 along the negative real axis to -∞, continuous from above.


template<class T> 
  complex<T> log (const complex<T>& z);


z Specify the complex number.

Return Value

Returns natural logarithm of z.


The example below shows the usage of log() function.

#include <iostream>
#include <complex>
using namespace std;
int main (){
  complex<double> z1 (2, 2);
  complex<double> z2 (2, 0);
  complex<double> z3 (0, 2);

  //calculate natural logarithm of given value
  cout<<"log(z1): "<<log(z1)<<"\n";
  cout<<"log(z2): "<<log(z2)<<"\n";
  cout<<"log(z3): "<<log(z3)<<"\n";

  return 0;

The output of the above code will be:

log(z1): (1.03972,0.785398)
log(z2): (0.693147,0)
log(z3): (0.693147,1.5708)

❮ C++ <complex> Library