isnormal() function in C++

In this tutorial, we are going to talk about the working of the isnormal() function in C++. As it is very much evident from its name, this function is used to find out whether a number is normal or not. A number is not normal if it is zero, infinite or NAN. Otherwise, the number is normal.

isnormal() function: Syntax and working

The isnormal() function() is defined in <cmath> header of C++. Its syntax would be like this.

bool isnormal(float num);
bool isnormal(double num);
bool isnormal(long double num);

As you can see, the function takes a floating-point value as an argument and returns a boolean value- 1(true) or 0(false). Let’s see more on this with example programs.

#include <iostream>
#include <cmath>

int main()
{
  float num = 5.0F;
  std::cout << num << " is " << (std::isnormal(num)? "normal" : "not normal" ) << std::endl;
  
  num = 0.0F;
  std::cout << num << " is " << (std::isnormal(num)? "normal" : "not normal")  << std::endl;
  
  num = 5.0F / 0.0F;
  std::cout << num << " is " << (std::isnormal(num)? "normal" : "not normal")  << std::endl;
  
  return 0;
}

The above C++ program gives the output:

5 is normal
0 is not normal
inf is not normal

Here, have a look at another example when arguments are passed as double.

#include <iostream>
#include <cmath>

int main()
{
  double num = 5.0;
  std::cout << num << " is " << (std::isnormal(num)? "normal" : "not normal" ) << std::endl;
  
  num = 0.0;
  std::cout << num << " is " << (std::isnormal(num)? "normal" : "not normal")  << std::endl;
  
  num = 5.0 / 0.0;
  std::cout << num << " is " << (std::isnormal(num)? "normal" : "not normal")  << std::endl;
  
  return 0;
}

Output:

5 is normal
0 is not normal
inf is not normal

In both of the above C++ programs, we have used isnormal() function to check whether the number passed as argument is normal or not. We have used a conditional operator in our program which prints “normal” if the function returns true otherwise it prints “not normal”. To understand the working of conditional operator see this article: Ternary Operator in C++

We can use isnormal() function with long double numbers as well.

Thank you.