The fdim() function in C is part of the standard math library <math.h> and is used to compute the positive difference between two floating-point numbers. This function is particularly useful when we need to determine the non-negative difference between two given values. It returns the difference between two values if the first value is greater than the second; otherwise, it returns zero.

Syntax of fdim() in C

double fdim(double x, double y);

Parameters of fdim() in C

The fdim() function in C takes the following parameters:

• x: The first floating-point number.
• y: The second floating-point number.

Return Value of fdim() in C

The fdim() function returns the positive difference between x and y. If x is greater than y, it returns x – y; otherwise, it returns 0.

Examples of fdim() Function in C

The below examples demonstrate how we can use the fdim() function in C language.

Input: 
double num1 = 5.5
double num2 = 3.2

Output:
The positive difference between 5.50 and 3.20 is: 2.30

Example 1

The below program demonstrates how to calculate the positive difference between two given numbers using the fdim() function in C.

// C Program to demonstrate the fdim() function

#include <math.h>
#include <stdio.h>

int main()
{
    // initialize numbers
    double x = 5.5, y = 3.2;
    // calculate result by calling fdim() function
    double result = fdim(x, y);

    // Print the result
    printf("The positive difference between %.2lf and "
           "%.2lf is: %.2lf\n",
           x, y, result);

    return 0;
}

The positive difference between 5.50 and 3.20 is: 2.30

Time Complexity: O(1)
Auxiliary Space: O(1)

Example 2

The following program demonstrates how to compute the positive difference for different data types in C.

// C program to demonstrate the fdim() function for
// different data types

#include <math.h>
#include <stdio.h>

int main()
{
    // initialize numbers
    double x1 = 5.5, y1 = 3.2;
    float x2 = 6.5f, y2 = 3.2f;
    long double x3 = 7.5l, y3 = 3.2l;

    // fdim function for double
    double result1 = fdim(x1, y1);

    // fdimf function for float
    float result2 = fdimf(x2, y2);

    // fdiml function for long double
    long double result3 = fdiml(x3, y3);

    // Print the results
    printf("The positive difference between %.2lf and "
           "%.2lf is: %.2lf\n",
           x1, y1, result1);
    printf("The positive difference between %.2f and %.2f "
           "is: %.2f\n",
           x2, y2, result2);
    printf("The positive difference between %.2Lf and "
           "%.2Lf is: %.2Lf\n",
           x3, y3, result3);

    return 0;
}

The positive difference between 5.50 and 3.20 is: 2.30
The positive difference between 6.50 and 3.20 is: 3.30
The positive difference between 7.50 and 3.20 is: 4.30

Time Complexity: O(1)
Auxiliary Space: O(1)

Note: The fdim() function is available in three variants: fdim() for double, fdimf() for float, and fdiml() for long double.