What is log1pf() in C?

The log1pf function is a C library function that returns the natural logarithm of the sum of one and the argument. For example, if the argument provided is x, the function calculates the natural logarithm of (1 + x), as shown below:

To use the log1pf function, we need to include the math.h header file, as shown below:

#include <math.h>

The log1pf function in C produces more accurate results than computing log(x + 1) separately.

Syntax

The log1pf function takes a single argument and returns a single value. It is declared as follows:

Parameter

The log1pf function takes a single argument of the float type.

Return Value

The log1pf function returns a single value of the float type:

  • If x is less than -1, a domain error occurs.

  • If x is equal to -1, a range error may occur.

  • If x is equal to 0, the return value will be 0.

Hence, arguments with values greater than -1 will produce correct results, i.e., the natural logarithm (1+x).

Example

The code below shows the use of the log1pf function in C:

#include <stdio.h>
#include <math.h>
int main() {
//Declare x
float x = 0.80;
//Call the function
float ans = log1pf (x);
//Display result
printf ("The natural log of (x+1) is: %f\n", ans);
return 0;
}
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