diff --git a/exercice_2/src/dumper_series.cc b/exercice_2/src/dumper_series.cc
index f3c6e88..687ce69 100644
--- a/exercice_2/src/dumper_series.cc
+++ b/exercice_2/src/dumper_series.cc
@@ -1,5 +1,9 @@
 #include "dumper_series.hh"
 
 DumperSeries::DumperSeries(Series &series) : series(series) {}
 
+void DumperSeries::setPrecision(unsigned int precision) {
+  this->precision = precision;
+}
+
 DumperSeries::~DumperSeries() = default;
diff --git a/exercice_2/src/dumper_series.hh b/exercice_2/src/dumper_series.hh
index f7f8203..1c7d270 100644
--- a/exercice_2/src/dumper_series.hh
+++ b/exercice_2/src/dumper_series.hh
@@ -1,18 +1,26 @@
 #ifndef DUMPER_SERIES_HH
 #define DUMPER_SERIES_HH
 
 #include "series.hh"
+#include <iostream>
 
 class DumperSeries {
 public:
   DumperSeries(Series &series);
   virtual ~DumperSeries();
 
 public:
-  virtual void dump() = 0;
+  virtual void dump(std::ostream &os) = 0;
+  virtual void setPrecision(unsigned int precision);
 
 protected:
   Series &series;
+  unsigned int precision;
 };
 
+inline std::ostream &operator<<(std::ostream &stream, DumperSeries &_this) {
+  _this.dump(stream);
+  return stream;
+}
+
 #endif
diff --git a/exercice_2/src/main.cc b/exercice_2/src/main.cc
index 8f9961d..9a8d025 100644
--- a/exercice_2/src/main.cc
+++ b/exercice_2/src/main.cc
@@ -1,60 +1,62 @@
 /* created by Marti Bosch and Marc Schwaerzel*/
 /* -------------------------------------------------------------------------- */
 #include <cstdlib>
 #include <cstring>
+#include <fstream>
 #include <iostream>
 #include <sstream>
 
 #include "compute_arithmetic.hh"
 #include "compute_pi.hh"
 #include "print_series.hh"
 #include "series.hh"
 #include "write_series.hh"
 
 using namespace std;
 /* -------------------------------------------------------------------------- */
 
 int main(int argc, char **argv) {
 
   if (argc != 5) {
     cout << "Arguments: frequency, maxiter, series_type (arithmetic, pi), "
             "dump_type (print, write)"
          << endl;
     return EXIT_FAILURE;
   }
 
   std::stringstream sstr;
   for (int i = 1; i < argc; ++i)
     sstr << argv[i] << " ";
 
   int frequency;
   int maxiter;
   std::string series_type;
   std::string dump_type;
 
   sstr >> frequency;
   sstr >> maxiter;
   sstr >> series_type;
   sstr >> dump_type;
 
   Series *series;
 
   if (series_type == "arithmetic")
     series = new ComputeArithmetic();
   else if (series_type == "pi")
     series = new ComputePi();
   else {
     std::cout << "input error" << std::endl;
     return EXIT_FAILURE;
   }
 
+  std::ofstream of("output.txt");
   if (dump_type == "print") {
     PrintSeries printseries(*series, maxiter, frequency);
-    printseries.dump();
+    printseries.dump(of);
   } else if (dump_type == "write") {
     WriteSeries writeseries(*series, maxiter, frequency);
-    writeseries.dump();
+    writeseries.dump(of);
   }
 
   delete series;
 }
diff --git a/exercice_2/src/print_series.cc b/exercice_2/src/print_series.cc
index c2afd2e..259cd9e 100644
--- a/exercice_2/src/print_series.cc
+++ b/exercice_2/src/print_series.cc
@@ -1,19 +1,21 @@
 #include "print_series.hh"
 #include <cmath>
+#include <iomanip>
 #include <iostream>
 
 PrintSeries::PrintSeries(Series &series, unsigned int maxiter,
                          unsigned int frequency)
     : DumperSeries(series), maxiter(maxiter), frequency(frequency) {}
 
-void PrintSeries::dump() {
+void PrintSeries::dump(std::ostream &os) {
   double analytic_prediction = this->series.getAnalyticPrediction();
   if (~std::isnan(analytic_prediction)) {
     for (int i = 1; i <= this->maxiter; i += this->frequency) {
       double value = this->series.compute(i);
-      std::cout << value << " / " << analytic_prediction << std::endl;
+      os << std::setprecision(this->precision) << value << " / "
+         << analytic_prediction << std::endl;
     }
   }
 }
 
 PrintSeries::~PrintSeries() = default;
diff --git a/exercice_2/src/print_series.hh b/exercice_2/src/print_series.hh
index 004ef0b..0388607 100644
--- a/exercice_2/src/print_series.hh
+++ b/exercice_2/src/print_series.hh
@@ -1,19 +1,19 @@
 #ifndef PRINT_SERIES_HH
 #define PRINT_SERIES_HH
 
 #include "dumper_series.hh"
 
 class PrintSeries : public DumperSeries {
 public:
   PrintSeries(Series &series, unsigned int maxiter, unsigned int frequency);
   virtual ~PrintSeries();
 
 public:
-  void dump();
+  void dump(std::ostream &os = std::cout);
 
 protected:
   unsigned int maxiter;
   unsigned int frequency;
 };
 
 #endif
diff --git a/exercice_2/src/write_series.cc b/exercice_2/src/write_series.cc
index d464941..15005c4 100644
--- a/exercice_2/src/write_series.cc
+++ b/exercice_2/src/write_series.cc
@@ -1,33 +1,33 @@
 #include "write_series.hh"
 #include <cmath>
 #include <fstream>
 
 WriteSeries::WriteSeries(Series &series, unsigned int maxiter,
                          unsigned int frequency)
     : DumperSeries(series), maxiter(maxiter), frequency(frequency),
       separator(" ") {}
 
-void WriteSeries::dump() {
-  std::string filepath("series");
+void WriteSeries::dump(std::ostream &os) {
   std::string separator = this->separator;
-  if (separator == ",")
-    filepath += ".csv";
-  else if (separator == "|")
-    filepath += ".psv";
-  else
-    filepath += ".txt";
-  std::ofstream f(filepath);
+  // std::string filepath("series");
+  // if (separator == ",")
+  //   filepath += ".csv";
+  // else if (separator == "|")
+  //   filepath += ".psv";
+  // else
+  //   filepath += ".txt";
+  // std::ofstream f(filepath);
   double analytic_prediction = this->series.getAnalyticPrediction();
   if (~std::isnan(analytic_prediction)) {
     for (int i = 1; i <= this->maxiter; i += this->frequency) {
       double value = this->series.compute(i);
-      f << value << separator << analytic_prediction << std::endl;
+      os << value << separator << analytic_prediction << std::endl;
     }
   }
 }
 
 void WriteSeries::setSeparator(std::string separator) {
   this->separator = separator;
 }
 
 WriteSeries::~WriteSeries() = default;
diff --git a/exercice_2/src/write_series.hh b/exercice_2/src/write_series.hh
index 61d9832..ce1f5f0 100644
--- a/exercice_2/src/write_series.hh
+++ b/exercice_2/src/write_series.hh
@@ -1,22 +1,22 @@
 #ifndef WRITE_SERIES_HH
 #define WRITE_SERIES_HH
 
 #include "dumper_series.hh"
 #include <string>
 
 class WriteSeries : public DumperSeries {
 public:
   WriteSeries(Series &series, unsigned int maxiter, unsigned int frequency);
   virtual ~WriteSeries();
 
 public:
-  void dump();
+  void dump(std::ostream &os);
   void setSeparator(std::string separator);
 
 protected:
   unsigned int maxiter;
   unsigned int frequency;
   std::string separator;
 };
 
 #endif