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/* $Id: prime.c,v 1.8 2006/05/12 23:38:15 joko Exp $ */ |
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|
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#include <stdio.h> |
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#include <stdlib.h> |
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#include <limits.h> |
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#include <errno.h> |
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|
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#define BOOL int |
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#define TRUE 1 |
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#define FALSE 0 |
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|
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#define PRINTPRIME(x) if (is_prime(x)) printf("%i\n", x) |
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#define PRINTERROR(message) fprintf(stderr, "ERROR: %s\n", message) |
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|
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/* check for prime number */ |
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BOOL is_prime(long int number) |
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{ |
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int i; |
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|
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/* negative values, 0 and 1 are never prime numbers */ |
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if (number < 2) return FALSE; |
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|
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/* check all numbers 2..sqrt(number) for being a prime number */ |
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for (i=2; i*i <= number; i++) { |
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if ((number % i) == 0) |
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return FALSE; |
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} |
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return TRUE; |
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} |
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|
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/* convert from string to long int, with error checking */ |
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long int convert_number(const char *nptr) { |
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|
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errno = 0; |
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char * endptr; |
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long int number = strtol(nptr, &endptr, 10); |
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|
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/* invalid characters? */ |
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if (*endptr != '\0') { |
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char message[254]; |
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snprintf(message, 256, "Could not convert '%s' to a valid number.", nptr); |
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PRINTERROR(message); |
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exit(EXIT_FAILURE); |
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} |
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|
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/* invalid range? */ |
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/* if (number == LONG_MAX || number == LONG_MIN) { */ |
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if (errno == ERANGE) { |
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char message[254]; |
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snprintf(message, 256, "Number is not in range of 'long int': %s", nptr); |
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PRINTERROR(message); |
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exit(EXIT_FAILURE); |
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} |
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|
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return number; |
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|
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} |
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|
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int main(int argc, char * argv[]) |
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{ |
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|
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if (argc == 1) { |
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PRINTERROR("No arguments given."); |
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exit(EXIT_FAILURE); |
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} |
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|
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/* (3) range mode */ |
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if (argc > 2) { |
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long int i, j; |
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i = convert_number(argv[1]); |
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j = convert_number(argv[2]); |
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for (i; i< j; i++) { |
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PRINTPRIME(i); |
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} |
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|
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/* other modes */ |
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} else { |
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|
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/* try to open file for reading */ |
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FILE * fp = fopen(argv[1], "r"); |
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|
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/* (1) test-single-number mode: first argument is not a filename */ |
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if (fp == NULL) { |
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long int number = convert_number(argv[1]); |
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PRINTPRIME(number); |
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|
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/* (2) file mode: read numbers from file */ |
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} else { |
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char entry[11]; |
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while (fgets(entry, 11, fp)) { |
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long int number = convert_number(entry); |
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PRINTPRIME(number); |
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} |
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fclose(fp); |
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} |
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} |
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} |