BSArch/01/prime.c

#include <stdio.h>

#define PRINTPRIME(x) if(is_prime(x)) printf("%i\n", x)
#define PRINTERROR(message) printf("ERROR: %s\n", message)

// check for prime number
int is_prime(int number)
{
        int i;
        for (i=2; i*i <= number; i++) {
                if ((number % i) == 0)
                        return 0;
        }
        return 1;
}

int main(int argc, char * argv[])
{
        
        // TODO: segfaults if zero arguments given
        // switch/case???
        if (argc == 1) {
                PRINTERROR("No arguments given, will segfault under cygwin. :-)");
        }
        
        // (3) range mode
        if (argc > 2) {
                int i, j;
                j = atoi(argv[2]);
                for (i = atoi(argv[1]); i< j; i++) {
                        PRINTPRIME(i);
                }
        
        // other modes
        } else {

                // try to open file for reading
                FILE * fp = fopen(argv[1], "r");
                
                // (1) test-single-number mode: first argument is not a filename
                if (fp == NULL) {
                        PRINTPRIME(atoi(argv[1]));
                
                // (2) file mode: read numbers from file
                } else {
                        char num[11];
                        while (fgets(num, 11, fp))
                                PRINTPRIME(atoi(num));
                        fclose(fp);
                }
        }
}
1	#include <stdio.h>
2
3	#define PRINTPRIME(x) if(is_prime(x)) printf("%i\n", x)
4	#define PRINTERROR(message) printf("ERROR: %s\n", message)
5
6	// check for prime number
7	int is_prime(int number)
8	{
9	int i;
10	for (i=2; i*i <= number; i++) {
11	if ((number % i) == 0)
12	return 0;
13	}
14	return 1;
15	}
16
17	int main(int argc, char * argv[])
18	{
19
20	// TODO: segfaults if zero arguments given
21	// switch/case???
22	if (argc == 1) {
23	PRINTERROR("No arguments given, will segfault under cygwin. :-)");
24	}
25
26	// (3) range mode
27	if (argc > 2) {
28	int i, j;
29	j = atoi(argv[2]);
30	for (i = atoi(argv[1]); i< j; i++) {
31	PRINTPRIME(i);
32	}
33
34	// other modes
35	} else {
36
37	// try to open file for reading
38	FILE * fp = fopen(argv[1], "r");
39
40	// (1) test-single-number mode: first argument is not a filename
41	if (fp == NULL) {
42	PRINTPRIME(atoi(argv[1]));
43
44	// (2) file mode: read numbers from file
45	} else {
46	char num[11];
47	while (fgets(num, 11, fp))
48	PRINTPRIME(atoi(num));
49	fclose(fp);
50	}
51	}
52	}
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