sqrt() -- Mathematics Function (libm)

Compute square root
#include <math.h>
double sqrt(z) double z;

sqrt() returns the square root of z.

Example

The following  program prints all prime numbers between  one and a positive
integer  that  the  user  enters.   It  was written  by  Michael  B.  Young
(myoung@mcs.csuhayward.edu).

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

int main()
{
    int i, userinput;

    /* get user input */
    fprintf(stderr, "Enter an integer value greater than 2:  ");
    scanf("%d", &userinput);

    if (userinput < 3) {
        fprintf(stderr, "Error:  enter a positive integer > 2\n");
        exit(EXIT_FAILURE);
    }

    /* test for all numbers between one and "userinput". */
    /* for efficiency's sake, even numbers are not tested. */
    /* two is the only even prime number */

    printf("%d\n", 2);
    for (i = 3; i < userinput; i += 2)
        if (prime(i))
            printf("%d\n", i);

    exit(EXIT_SUCCESS);
}

/*
 *  function prime() - tests the passed integer testvalue for "prime-ness"
 *  by testing whether each integer between 1 and the square root of
 *  testvalue divides evenly into testvalue.  Returns 1 if prime, 0 if not.
 */
int prime(testvalue)
int testvalue;
{
    int end, j, result;

    end = (int) sqrt ( (double) testvalue );
    for (j = 2, result = 1; result == 1 && j <= end; j++) {
        if ((testvalue % j) == 0)
            result = 0;
    }
    return result;
}

See Also

cos(),
cosh(),
libm,
sin()
ANSI Standard, §7.5.5.2
POSIX Standard, §8.1

Diagnostics

When a domain error occurs (i.e., when z is negative), sqrt() sets errno to
EDOM and returns zero.

© 2012 by Stephen A. Ness