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valarray log() function in C++

  • Last Updated : 24 Oct, 2018

The log() function is defined in valarray header file. This function is used to calculate natural logarithm of the value of the elements in valarray.
Syntax:

log(varr);

Parameter: This function takes a mandatory parameter varr which represents valarray.

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Returns: This function returns a valarray containing the natural logarithm of all the elements.

Below programs illustrate the above function:



Example 1:-




// C++ program to demonstrate
// example of log() function.
  
#include<bits/stdc++.h>
using namespace std; 
int main() 
    // Initializing valarray 
    valarray<double>
 varr = { 1, 2, 3, 4, 5 }; 
        
    // Declaring new valarray 
    valarray<double> varr1 ; 
        
    // use of log() function 
    varr1 = log(varr); 
        
    // Displaying new elements value
    cout << "The new valarray with"
         << " manipulated values is : "
         << endl;
  
    for (double& x : varr1) {
        cout << x << " ";
    }
  
    cout << endl;
  
    return 0;
Output:
The new valarray with manipulated values is : 
0 0.693147 1.09861 1.38629 1.60944

Example 2:-




// C++ program to demonstrate
// example of log() function.
  
#include<bits/stdc++.h>
using namespace std; 
int main() 
    // Initializing valarray 
    valarray<double>
 varr = { -1, 6, 3, 45, 5 }; 
        
    // Declaring new valarray 
    valarray<double> varr1 ; 
        
    // use of log() function 
    varr1 = log(varr); 
        
    // Displaying new elements value
    cout << "The new valarray with"
         << " manipulated values is : "
         << endl;
  
    for (double& x : varr1) {
        cout << x << " ";
    }
  
    cout << endl;
  
    return 0;
Output:
The new valarray with manipulated values is : 
nan 1.79176 1.09861 3.80666 1.60944



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