+int string_to_positive_integer(char *string) {
+ int error = 0;
+ int result = 0;
+
+ if(*string) {
+ for(char *s = string; *s; s++) {
+ if(*s >= '0' && *s <= '9') {
+ result = result * 10 + int(*s - '0');
+ } else error = 1;
+ }
+ } else error = 1;
+
+ if(error) {
+ cerr << "Value `" << string << "' is not a positive integer." << endl;
+ exit(1);
+ }
+
+ return result;
+}
+