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isless() Function with Example in C++

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

C++ isless() function

isless() function is a library function of cmath header, it is used to check whether the given first value is less than the second value. It accepts two values (float, double or long double) and returns 1 if the first value is less than the second value; 0, otherwise.

Syntax of isless() function:

In C99, it has been implemented as a macro,

    macro isless(x, y)

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

    bool isless (float x      , float y);
    bool isless (double x     , double y);
    bool isless (long double x, long double y);

Parameter(s):

x, y – represent the two values to be checked whether x is less than the y.

Return value:

The returns type of this function is bool, it returns 1 if x is less than y; 0, otherwise.

Example:

    Input:
    float x = 5.0f;
    float y = 15.0f;
    
    Function call:
    isless(x, y);
    
    Output:
    1

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

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

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

int main()
{
    cout << "isless(0.0f, -2.0f)   : " << isless(0.0f, -2.0f) << endl;
    cout << "isless(10.0f, 20.0f)  : " << isless(10.0f, 20.0f) << endl;
    cout << "isless(10.0f, 5.0f)   : " << isless(10.0f, 5.0f) << endl;
    cout << "isless(-10.0f, -20.0f): " << isless(-10.0f, -20.0f) << endl;

    float x = 10.0f;
    float y = 5.0f;

    // checking using the condition
    if (isless(x, y)) {
        cout << x << " is less than " << y << endl;
    }
    else {
        cout << x << " is not less than " << y << endl;
    }

    x = 9.0f;
    y = 10.0f;

    if (isless(x, y)) {
        cout << x << " is less than " << y << endl;
    }
    else {
        cout << x << " is not less than " << y << endl;
    }

    return 0;
}

Output

isless(0.0f, -2.0f)   : 0
isless(10.0f, 20.0f)  : 1
isless(10.0f, 5.0f)   : 0
isless(-10.0f, -20.0f): 0
10 is not less than 5
9 is less than 10