--- joko/Uni/BSArch/01/prime.c	2006/05/12 19:53:48	1.4
+++ joko/Uni/BSArch/01/prime.c	2006/05/12 23:27:11	1.7
@@ -1,51 +1,77 @@
+/* $Id: prime.c,v 1.7 2006/05/12 23:27:11 joko Exp $ */
+
 #include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+#define BOOL int
+#define TRUE 1
+#define FALSE 0
 
-#define PRINTPRIME(x) if(is_prime(x)) printf("%i\n", x)
-#define PRINTERROR(message) printf("ERROR: %s\n", message)
+#define PRINTPRIME(x) if (is_prime(x)) printf("%i\n", x)
+#define PRINTERROR(message) fprintf(stderr, "ERROR: %s\n", message)
 
-// check for prime number
-int is_prime(int number)
+/* check for prime number */
+BOOL is_prime(long int number)
 {
 	int i;
+	
+	/* negative values are never prime numbers */
+	if (number < 2) return FALSE;
+	
+	/* check all numbers 2..sqrt(number) for being a prime number */
 	for (i=2; i*i <= number; i++) {
 		if ((number % i) == 0)
-			return 0;
+			return FALSE;
+	}
+	return TRUE;
+}
+
+/* convert from string to long int, with error checking */
+long int convert_number(const char *nptr) {
+	long int number = strtol(nptr, (char **)NULL, 10);
+	if (number == LONG_MAX || number == LONG_MIN) {
+		char message[254];
+		snprintf(message, 255, "Number is not in range of 'long int': %s", nptr);
+		PRINTERROR(message);
+		exit(-1);
 	}
-	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. :-)");
+		PRINTERROR("No arguments given.");
+		exit(-1);
 	}
 	
-	// (3) range mode
+	/* (3) range mode */
 	if (argc > 2) {
-		int i, j;
-		j = atoi(argv[2]);
-		for (i = atoi(argv[1]); i< j; i++) {
+		long int i, j;
+		j = convert_number(argv[2]);
+		for (i = convert_number(argv[1]); i< j; i++) {
 			PRINTPRIME(i);
 		}
 	
-	// other modes
+	/* other modes */
 	} else {
 
-		// try to open file for reading
+		/* try to open file for reading */
 		FILE * fp = fopen(argv[1], "r");
 		
-		// (1) test-single-number mode: first argument is not a filename
+		/* (1) test-single-number mode: first argument is not a filename */
 		if (fp == NULL) {
-			PRINTPRIME(atoi(argv[1]));
+			long int number = convert_number(argv[1]);
+			PRINTPRIME(number);
 		
-		// (2) file mode: read numbers from file
+		/* (2) file mode: read numbers from file */
 		} else {
-			char num[11];
-			while (fgets(num, 11, fp))
-				PRINTPRIME(atoi(num));
+			char entry[11];
+			while (fgets(entry, 11, fp)) {
+				long int number = convert_number(entry);
+				PRINTPRIME(number);
+			}
 			fclose(fp);
 		}
 	}