isgreater() in C/C++

In C programming, the isgreater() function is a type-generic macro used to compare two floating-point values safely. It is declared in the <math.h> header file and returns a non-zero value (true) if the first argument is greater than the second, otherwise returns 0 (false). Unlike the regular > operator, isgreater() never raises floating-point exceptions.

Syntax

int isgreater(x, y);

Parameters:

• x − First floating-point value to compare
• y − Second floating-point value to compare

Return Value: Returns 1 if x is greater than y, otherwise returns 0.

Example 1: Basic Usage with Float Values

Here's a simple example demonstrating isgreater() with floating-point numbers −

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

int main() {
    float val1 = 28.5;
    float val2 = 8.3;
    int result;
    
    result = isgreater(val1, val2);
    printf("isgreater(%.1f, %.1f) = %d\n", val1, val2, result);
    
    result = isgreater(val2, val1);
    printf("isgreater(%.1f, %.1f) = %d\n", val2, val1, result);
    
    return 0;
}

isgreater(28.5, 8.3) = 1
isgreater(8.3, 28.5) = 0

Example 2: Comparing with Special Values

The isgreater() function handles special floating-point values like NaN safely −

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

int main() {
    double a = 5.0;
    double b = 3.0;
    double nan_val = 0.0/0.0;  // NaN
    
    printf("isgreater(5.0, 3.0) = %d\n", isgreater(a, b));
    printf("isgreater(3.0, 5.0) = %d\n", isgreater(b, a));
    printf("isgreater(5.0, NaN) = %d\n", isgreater(a, nan_val));
    printf("isgreater(NaN, 5.0) = %d\n", isgreater(nan_val, a));
    
    return 0;
}

isgreater(5.0, 3.0) = 1
isgreater(3.0, 5.0) = 0
isgreater(5.0, NaN) = 0
isgreater(NaN, 5.0) = 0

Key Points

• The isgreater() function is exception-safe and never raises floating-point exceptions.
• It returns 0 when either operand is NaN, making it safer than the > operator.
• It works with float, double, and long double types.
• The function is implemented as a type-generic macro.

Conclusion

The isgreater() function provides a safe way to compare floating-point values without triggering exceptions. It is particularly useful when dealing with special values like NaN or when exception-safe code is required.