nextafter() and nexttoward() in C/C++
How would you solve below problems in C/C++?
- What is the smallest representable positive floating point number in C/C++?
- What is the largest representable negative floating point number in C/C++?
- Given a positive floating point number x, find the largest representable floating point value smaller than x?
nextafter(x, y) and nexttoward(x.y)
In C and C++, both nextafter(x, y) and nexttoward(x.y) are similar functions defined in math.h or cmath header files. They both return next representable value after x in the direction of y. nexttoward() has more precise second parameter y.
The following program demonstrates the concept :
// C program to demonstrate use of nextafter() and nexttoward()#include <stdio.h>#include <math.h>int main (){ // using nextafter printf ("Smallest positive floating point number : %e\n", nextafter(0.0, 1.0)); printf ("Largest negative floating point number :%e\n", nextafter(0.0, -1.0)); printf ("Largest positive floating point number smaller than 0.5 : %e\n", nextafter(0.5, 0.0)); // using nexttoward printf ("Smallest positive floating point number : %e\n", nexttoward(0.0, 1.0)); printf ("Largest negative floating point number : %e\n", nexttoward(0.0, -1.0)); printf ("Largest positive floating point number smaller than 0.5 : %e\n", nexttoward(0.5, 0.0)); return (0);} |
Output:
nextafter first value greater than zero: 4.940656e-324 nextafter first value less than zero: -4.940656e-324 nexttoward first value greater than zero: 4.940656e-324 nexttoward first valnextafter first value greater than zero: 4.940656e-324 nextafter first value less than zero: -4.940656e-324 nexttoward first value greater than zero: 4.940656e-324 nexttoward first value less than zero: -4.940656e-324 ue less than zero: -4.940656e-324
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