/* * File: primes2.c                  (WARNING -- BUGGY PROGRAM) * --------------- * This program prints out a list of all prime numbers between * the limits LowerLimit and UpperLimit.  This version attempts * to use a more efficient algorithm than the one in primes.c * to implement the IsPrime function, but the result is both * buggy for certain argument values and surprisingly inefficient * when it does work. */#include <stdio.h>#include <math.h>#include "genlib.h"/* * Constants * --------- * LowerLimit -- Starting value for the prime search * UpperLimit -- Final value for the prime search */#define LowerLimit 0#define UpperLimit 1000/* Function prototypes */bool IsPrime(int n);/* Main program */main(){    int i;    printf("This program lists the primes between %d and %d.\n",           LowerLimit, UpperLimit);    for (i = LowerLimit; i <= UpperLimit; i++) {        if (IsPrime(i)) {            printf("%4d\n", i);        }    }}/* * Function: IsPrime * Usage: if (IsPrime(n)) . . . * ---------------------------- * Returns TRUE if n is prime, and FALSE otherwise.  The * implementation takes account of the following observations: * * 1.  Even numbers are not prime (with the exception of *     2, which this buggy program incorrectly classifies). * * 2.  If the only concern of the function is determining *     whether the number is prime, there is no reason to *     continue the loop after a factor is found. * * 3.  If a number n has a factor f larger than the square root *     of n, then n/f must also be a factor and must be smaller *     than the square root of n.  Thus, it is sufficient to *     check only factors up to the square root. */bool IsPrime(int n){    int i;    if (n % 2 == 0) return (FALSE);    for (i = 3; i <= sqrt(n); i += 2) {        if (n % i == 0) return (FALSE);    }    return (TRUE);}