added error messages

IntToFile.cpp

@@ -9,6 +9,7 @@
  ***********************************************************************************************************************/
 
 #include "IntToFile.hpp"
+#include <iostream>
 
 /***********************************************************************************************************************
  *  public static function definitions
@@ -23,11 +24,13 @@ void IntToFile::AppendInt(std::string filename, int num) {
 
 	// error opening file
 	if (file == nullptr) {
+		std::cerr << "Error occured while opening file. Possibly an unclosed file." << std::endl;
 		return;
 	}
 
 	// trigger pseudo error (negative numbers not allowed)
 	if (num < 0) {
+		std::cerr << "Error: no negative numbers allowed!" << std::endl;
 		return;
 	}