C++ Valarray Library - log Function

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Description

It returns a valarray containing the natural logarithm (base-e logarithm) of all the elements of x, in the same order.

Declaration

Following is the declaration for std::log function.

template<class T> valarray<T> log (const valarray<T>& x);

C++11

template<class T> valarray<T> log (const valarray<T>& x);

Parameters

x − It is containing elements of a type for which the unary function abs is defined.

Return Value

It returns a valarray containing the natural logarithm (base-e logarithm) of all the elements of x, in the same order.

Exceptions

Basic guarantee − if any operation performed on the elements throws an exception.

Data races

All elements effectively copied are accessed.

Example

In below example explains about std::log function.

#include <iostream>
#include <cstddef>
#include <cmath>
#include <valarray>

int main () {
   double val[] = {5.0, 6.0, 8.0, 9.5};
   std::valarray<double> foo (val,4);

   std::valarray<double> bar = log (foo);

   std::cout << "foo:";
   for (std::size_t i=0; i<foo.size(); ++i)
      std::cout << ' ' << foo[i];
   std::cout << '\n';

   std::cout << "bar:";
   for (std::size_t i=0; i<bar.size(); ++i)
      std::cout << ' ' << bar[i];
   std::cout << '\n';

   return 0;
}

Let us compile and run the above program, this will produce the following result −

foo: 5 6 8 9.5
bar: 1.60944 1.79176 2.07944 2.25129