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isinf() Function with Example in C++

C++ isinf() function: Here, we are going to learn about the isinf() function with example of cmath header in C++ programming language?
Submitted by IncludeHelp, on May 17, 2020

C++ isinf() function

isinf() function is a library function of cmath header, it is used to check whether the given value is infinite (negative infinity or positive infinity). It accepts a value (float, double or long double) and returns 1 if the given value is an infinity; 0, otherwise.

Syntax of isinf() function:

In C99, it has been implemented as a macro,

    macro isinf(x)

In C++11, it has been implemented as a function,

    bool isinf (float x);
    bool isinf (double x);
    bool isinf (long double x);

Parameter(s):

x – represents the value to be checked whether x is an infinity or not.

Return value:

The returns type of this function is bool, it returns 1 if x is an infinity; 0, otherwise.

Example:

    Input:
    float x = 10.0f/0.0f;
    
    Function call:
    isinf(x);
    
    Output:
    1

C++ code to demonstrate the example of isinf() function

// C++ code to demonstrate the example of
// isinf() function

#include <iostream>
#include <cmath>
using namespace std;

int main()
{
    cout << "isinf(1.0f/0.0f)  : " << isinf(1.0f / 0.0f) << endl;
    cout << "isinf(-1.0f/-0.0f): " << isinf(-1.0f / -0.0f) << endl;
    cout << "isinf(0.0/1.0)    : " << isinf(0.0 / 1.0) << endl;
    cout << "isinf(1.0/0.0)    : " << isinf(1.0 / 0.0) << endl;

    float x = 10.0f;

    // checking using the condition
    if (isinf(x)) {
        cout << x << " is infinite value." << endl;
    }
    else {
        cout << x << " is not infinite value." << endl;
    }

    x = 10.0f / 0.0f;

    if (isinf(x)) {
        cout << x << " is infinite value." << endl;
    }
    else {
        cout << x << " is not infinite value." << endl;
    }

    return 0;
}

Output

isinf(1.0f/0.0f)  : 1
isinf(-1.0f/-0.0f): 1
isinf(0.0/1.0)    : 0
isinf(1.0/0.0)    : 1
10 is not infinite value.
inf is infinite value.