ilogb() Function in C
The ilogb() function in C is a part of the standard math library <math.h>. It is used to compute the binary exponent of a floating-point number, which is the exponent of the value when represented as a normalized floating-point number. This function is particularly useful for numerical analysis and floating-point arithmetic.
Syntax of ilogb() in C
int ilogb(double x);
Parameters of ilogb() in C
The ilogb() function in C takes the following parameter:
- x: The floating-point number whose binary exponent is to be computed.
Return Value of ilogb() in C
The ilogb() function returns the exponent part of the logarithm (base 2) of the floating-point number x.
- For normalized numbers, it returns the unbiased exponent.
- For subnormal numbers, it returns the exponent of the normalized equivalent.
- For zero, it returns FP_ILOGB0.
- For infinity, it returns INT_MAX.
- For NaN, it returns FP_ILOGBNAN.
Examples of ilogb() Function in C Language
The below examples demonstrate how we can use the ilogb() function in C language.
Input:
double x = 1.5
Output:
The binary exponent of 16.00 is: 4
Example 1
The following program demonstrates how to use the ilogb() function in C.
// C Program to demonstrate the ilogb() function
#include <math.h>
#include <stdio.h>
int main()
{
// initialize the double value
double x = 16.0;
// call the ilogb() function
int result = ilogb(x);
// Print the result
printf("The binary exponent of %.2lf is: %d\n", x,
result);
return 0;
}
Output
The binary exponent of 16.00 is: 4
Time Complexity: O(1)
Auxiliary Space: O(1)
Example 2
The following program demonstrates how to handle special values using ilogb() function in C.
// C Program demonstrating ilogb() for special values
#include <math.h>
#include <stdio.h>
int main()
{
// initialize all the special values
double x1 = 0.0;
double x2 = INFINITY;
double x3 = NAN;
double x4 = 0.25;
// ilogb function for various values
int result1 = ilogb(x1);
int result2 = ilogb(x2);
int result3 = ilogb(x3);
int result4 = ilogb(x4);
// Print the results
printf("The exponent part of log2(0.0) is: %d "
"(FP_ILOGB0)\n",
result1);
printf("The exponent part of log2(INFINITY) is: %d "
"(INT_MAX)\n",
result2);
printf("The exponent part of log2(NAN) is: %d "
"(FP_ILOGBNAN)\n",
result3);
printf("The exponent part of log2(0.25) is: %d\n",
result4);
return 0;
}
Output
The exponent part of log2(0.0) is: -2147483648 (FP_ILOGB0)
The exponent part of log2(INFINITY) is: 2147483647 (INT_MAX)
The exponent part of log2(NAN) is: -2147483648 (FP_ILOGBNAN)
The exponent part of log2(0.25) is: -2
Time Complexity: O(1)
Auxiliary Space: O(1)
Example 3
The following program demonstrates how to find the binary exponent for different data types in C.
// C program to demonstrate the ilogb() function for
// different data types
#include <math.h>
#include <stdio.h>
int main()
{
// initialize values of different data types
double x1 = 16.0;
float x2 = 25.0f;
long double x3 = 36.0l;
// ilogb function for double
int result1 = ilogb(x1);
// ilogbf function for float
int result2 = ilogbf(x2);
// ilogbl function for long double
int result3 = ilogbl(x3);
// Print the results
printf("The binary exponent of %.2lf is: %d\n", x1,
result1);
printf("The binary exponent of %.2f is: %d\n", x2,
result2);
printf("The binary exponent of %.2Lf is: %d\n", x3,
result3);
return 0;
}
Output
The binary exponent of 16.00 is: 4 The binary exponent of 25.00 is: 4 The binary exponent of 36.00 is: 5
Time Complexity: O(1)
Auxiliary Space: O(1)
