--- joko/Uni/BSArch/01/prime.c	2006/05/12 18:41:34	1.1
+++ joko/Uni/BSArch/01/prime.c	2006/05/12 23:38:15	1.8
@@ -1,32 +1,77 @@
+/* $Id: prime.c,v 1.8 2006/05/12 23:38:15 joko Exp $ */
+
 #include <stdio.h>
-#include <math.h>
-#define PRINTPRIME(x) if(prime(x)) printf("%i\n", x)
-int prime(int number)
+#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) fprintf(stderr, "ERROR: %s\n", message)
+
+/* check for prime number */
+BOOL is_prime(long int number)
 {
-  int i;
-  for(i=2;i*i<=number;i++){
-  	if((number%i) == 0)
-	  return 0;
-  }
-  return 1;
+	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 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, 256, "Number is not in range of 'long int': %s", nptr);
+		PRINTERROR(message);
+		exit(-1);
+	}
 }
+
 int main(int argc, char * argv[])
 {
-	int i, j;
-	FILE * fp;
-	char num[11];
-	if(argc > 2 ){
-		j=atoi(argv[2]);
-		for(i=atoi(argv[1]) ; i< j; i++){
+	
+	if (argc == 1) {
+		PRINTERROR("No arguments given.");
+		exit(-1);
+	}
+	
+	/* (3) range mode */
+	if (argc > 2) {
+		long int i, j;
+		j = convert_number(argv[2]);
+		for (i = convert_number(argv[1]); i< j; i++) {
 			PRINTPRIME(i);
 		}
-	}else {
-		fp=fopen(argv[1], "r");
-		if(fp==NULL){
-			PRINTPRIME(atoi(argv[1]));
-		}else{
-			while(fgets(num, 11, fp))
-				PRINTPRIME(atoi(num));
+	
+	/* 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) {
+			long int number = convert_number(argv[1]);
+			PRINTPRIME(number);
+		
+		/* (2) file mode: read numbers from file */
+		} else {
+			char entry[11];
+			while (fgets(entry, 11, fp)) {
+				long int number = convert_number(entry);
+				PRINTPRIME(number);
+			}
 			fclose(fp);
 		}
 	}