diff --git a/homework2/homework2.kdev4 b/homework2/homework2.kdev4
deleted file mode 100644
index aba3115..0000000
--- a/homework2/homework2.kdev4
+++ /dev/null
@@ -1,3 +0,0 @@
-[Project]
-Manager=KDevCMakeManager
-Name=homework2
diff --git a/homework2/src/dumper_series.h b/homework2/src/dumper_series.h
index 122089e..3d1c198 100644
--- a/homework2/src/dumper_series.h
+++ b/homework2/src/dumper_series.h
@@ -1,18 +1,19 @@
 
 #ifndef DUMPER_SERIES
 #define DUMPER_SERIES
 
 #include "Series.hh"
+#include <iostream>
 
 class DumperSeries{
   public:
     DumperSeries(Series & series):
     series(series){}
-    virtual void dump() = 0;
+    virtual void dump(std::ostream & os) = 0;
 
   protected:
     Series & series;
 
 };
 
 #endif
diff --git a/homework2/src/main.cc b/homework2/src/main.cc
index 13f8cc2..54a8fea 100644
--- a/homework2/src/main.cc
+++ b/homework2/src/main.cc
@@ -1,68 +1,74 @@
 //main
 
 #include "ComputeArithmetic.hh"
 #include "ComputePi.hh"
 #include "print_series.h"
 #include "write_series.h"
 #include <iostream>
 #include <sstream>
+#include <fstream>
 #include <stdlib.h>
 
 using namespace std;
 
 int main(int argc, char ** argv){
 
     //command line arguments: Type of series and N of terms.
 
     stringstream sstr;
     for (int i = 1 ; i < argc ; ++i){
         sstr << argv[i] << " ";
     }
 
     string which_series;
     string which_dumper;
     int frequency;
     int maxiter;
     sstr >> which_series;
     sstr >> which_dumper;
     sstr >> frequency;
     sstr >> maxiter;
 
     Series * my_series = NULL;
     DumperSeries * my_dumper = NULL;
 
     if (which_series == "pi")
         my_series = new ComputePi();
     else if (which_series == "arithmetic")
         my_series = new ComputeArithmetic();
     else {
         cout<<"insert one of the two available options:"
               "\n\t arithmetic (to compute arithmetic series)"
               "\n\t pi (to compute Pi series)"<<endl;
         return EXIT_FAILURE;
     }
 
-    if (which_dumper == "print")
+    std::ostream * os = &std::cout;;
+    if (which_dumper == "print"){
         my_dumper = new PrintSeries(*my_series, frequency, maxiter);
-    else if (which_dumper == "write"){
+    }else if (which_dumper == "write"){
         std::string separator;
-	sstr >> separator;
+        sstr >> separator;
         my_dumper = new WriteSeries(*my_series, frequency, maxiter, separator);
     }else {
         cout<<"insert one of the two available options:"
               "\n\t print (to print on screen)"
               "\n\t write (to write in file)"<<endl;
         return EXIT_FAILURE;
     }
 
-    my_dumper->dump();
+    std::string file_name = "data.txt";
+    std::ofstream file(file_name.c_str());
+    os = & file;
+    my_dumper->dump(*os);
 
+    file.close();
 
     //double tmpi = my_series->compute(N);
 
     //cout<<"Result for the "<<which_series<<" series with "<<N<<" terms is "<< tmp<<endl;
 
     delete my_series;
     delete my_dumper;
     return 0;
 }
diff --git a/homework2/src/print_series.cc b/homework2/src/print_series.cc
index 926ed6a..9a78349 100644
--- a/homework2/src/print_series.cc
+++ b/homework2/src/print_series.cc
@@ -1,22 +1,22 @@
 #include "print_series.h"
 
 PrintSeries::PrintSeries(Series & series, int frequency, int maxiter):
   DumperSeries(series){
   this->frequency = frequency;
   this->maxiter = maxiter;
 }
 
-void PrintSeries::dump(){
+void PrintSeries::dump(std::ostream & os){
   for(int i=frequency; i<maxiter; i += frequency){
     double value = series.compute(frequency);
-    std::cout<<"i == "<<i<<" , series == "<<value;
+    os<<"i == "<<i<<" , series == "<<value;
     double analytic_value = 3.0;// series.getAnalyticPrediction();
     if(analytic_value != analytic_value){
-      std::cout<<std::endl;
+      os<<std::endl;
     }else{
       double convergence_percent = (value/analytic_value) * 100.0;
-      std::cout<<" , convergence percent == "<<convergence_percent<<std::endl;
+      os<<" , convergence percent == "<<convergence_percent<<std::endl;
     }
   }
 }
   
diff --git a/homework2/src/print_series.h b/homework2/src/print_series.h
index 6f12cc1..a0c558c 100644
--- a/homework2/src/print_series.h
+++ b/homework2/src/print_series.h
@@ -1,18 +1,17 @@
 
 #ifndef PRINT_SERIES
 #define PRINT_SERIES
 
 #include "dumper_series.h"
-#include <iostream>
 
 class PrintSeries: public DumperSeries{
   public:
     PrintSeries(Series & series, int frequency, int maxiter);
-    void dump() override;
+    void dump(std::ostream & os = std::cout) override;
 
   private:
     int frequency;
     int maxiter;
 };
 
 #endif
diff --git a/homework2/src/write_series.cc b/homework2/src/write_series.cc
index e624832..e674607 100644
--- a/homework2/src/write_series.cc
+++ b/homework2/src/write_series.cc
@@ -1,45 +1,49 @@
 #include "write_series.h"
 #include <fstream>
   
 WriteSeries::WriteSeries(Series & series, int frequency, int maxiter, std::string separator):
   DumperSeries(series){
   this->frequency = frequency;
   this->maxiter = maxiter;
   setSeparator(separator);
 }
 
-void WriteSeries::dump(){
-  std::string file_name = "data" + file_extension;
-  std::ofstream file(file_name.c_str());
-  file<<"#i"<<separator<<"value"<<separator<<"convergence_percent"<<std::endl;
+void WriteSeries::dump(std::ostream & os){
+  
+  //std::string file_name = "data" + file_extension;  // for ex 3.7
+  //std::ofstream os(file_name.c_str());
+  
+  os<<"#i"<<separator<<"value"<<separator<<"convergence_percent"<<std::endl;
   for(int i=frequency; i<maxiter; i += frequency){
     double value = series.compute(frequency);
-    file<<i<<separator<<value;
-    double analytic_value = 3;//series.getAnalyticPrediction();
-    if(analytic_value != analytic_value){
-      file<<std::endl;
+    os<<" "<<i<<separator<<value;
+    double analytic_value = series.getAnalyticPrediction();
+    if(analytic_value != analytic_value){  //IEEE standard: NAN != NAN
+      os<<std::endl;
     }else{
       double convergence = (value/analytic_value) * 100.0;  //percent
-      file<<separator<<convergence<<std::endl;
+      os<<separator<<convergence<<std::endl;
     }
   }
-  file.close();
+  
+  //file.close();
+
 }
 
 void WriteSeries::setSeparator(std::string separator){
   if(separator == "comma"){
     this->separator = ",";
     this->file_extension = ".csv";
   }else if(separator == "space"){
     this->separator = " ";
     this->file_extension = ".txt";
   }else if(separator == "tab"){
     this->separator = "\t";
     this->file_extension = ".txt";
   }else if(separator == "pipe"){
     this->separator = "|";
     this->file_extension = ".psv";
   }else{
-    std::cerr<<"Not known separator!!! please choose one of {comma, space, tab, pipe}.";
+    std::cerr<<"Not known separator!!! please choose one of {comma, space, tab, pipe}."<<std::endl;
   }
-}
+}
\ No newline at end of file
diff --git a/homework2/src/write_series.h b/homework2/src/write_series.h
index 64f20d0..0f738fe 100644
--- a/homework2/src/write_series.h
+++ b/homework2/src/write_series.h
@@ -1,21 +1,20 @@
 
 #ifndef WRITE_SERIES
 #define WRITE_SERIES
 
 #include "dumper_series.h"
-#include <iostream>
   
 class WriteSeries: public DumperSeries{
   public:
-    WriteSeries(Series & series, int frequency, int maxiter, std::string separator);
-    void dump() override;
+    WriteSeries(Series & series, int frequency, int maxiter, std::string separator = "tab");
+    void dump(std::ostream & os) override;
     void setSeparator(std::string separator);
 
   private:
     int frequency;
     int maxiter;
     std::string separator;
     std::string file_extension;
 };
 
 #endif