diff --git a/trunk/src/clusterization.h b/trunk/src/clusterization.h
index 183faab..b613fdb 100644
--- a/trunk/src/clusterization.h
+++ b/trunk/src/clusterization.h
@@ -16,7 +16,8 @@ class clusterization: public category::kleisli::arr<boost::shared_ptr<T>, boost:
         }
     };
     typedef boost::shared_ptr<category::kleisli::end<T_ptr> > Cont;
-    std::map<T_ptr, Cont, less> _continuations;
+    typedef std::map<T_ptr, Cont, less> map;
+    map _continuations;
 public:
     void next(const T_ptr& t) {
         typename std::map<T_ptr, Cont, less>::iterator it = _continuations.find(t);
@@ -28,6 +29,12 @@ class clusterization: public category::kleisli::arr<boost::shared_ptr<T>, boost:
             it->second->next(t);
         }
     }
+    void stop() {
+        for (typename map::iterator it = _continuations.begin(); it != _continuations.end(); ++it) {
+            it->second->stop();
+        }
+        _continuations.clear();
+    }
 };
 
 #endif
diff --git a/trunk/src/comparator.h b/trunk/src/comparator.h
new file mode 100644
index 0000000..629b13f
--- /dev/null
+++ b/trunk/src/comparator.h
@@ -0,0 +1,43 @@
+#ifndef _COMPARATOR_H_
+#define _COMPARATOR_H_
+
+#include <boost/shared_ptr.hpp>
+#include <vector>
+
+#include "kleisli.h"
+#include "type_list.h"
+
+template<typename T, typename C>
+class comparator: public category::kleisli::arr<boost::shared_ptr<T>, boost::shared_ptr<C> > {
+    typedef boost::shared_ptr<T> T_ptr;
+    typedef boost::shared_ptr<C> C_ptr;
+    typedef boost::shared_ptr< category::kleisli::end<C_ptr> > Cont;
+    typedef std::vector< std::pair<T_ptr, Cont> > vector;
+    vector _values;
+public:
+    void next(const T_ptr& t) {
+        for (typename vector::iterator it = _values.begin(); it != _values.end(); ++it) {
+            C_ptr r = it->first->compare(t);
+            if (r) {
+                it->second->next(r);
+                return;
+            }
+        }
+        Cont cont = category::kleisli::sink<C_ptr>::continuation().clone();
+        if (SUPER_SUB_CLASS(C, T)) {
+            cont->next(t);
+        }
+        _values.push_back(std::make_pair(t, cont));
+    }
+    void stop() {
+        for (typename vector::iterator it = _values.begin(); it != _values.end(); ++it) {
+            it->second->stop();
+        }
+        _values.clear();
+    }
+    boost::shared_ptr< category::kleisli::end<T_ptr> > clone() const {
+        return boost::make_shared< comparator<T, C> >(*this);
+    }
+};
+
+#endif
diff --git a/trunk/src/default_main.cpp b/trunk/src/default_main.cpp
index cd066f3..3cd71c3 100644
--- a/trunk/src/default_main.cpp
+++ b/trunk/src/default_main.cpp
@@ -1,5 +1,4 @@
-#include <boost/shared_ptr.hpp>
-
+#include "comparator.h"
 #include "clusterization.h"
 #include "program_options.h"
 #include "filesystem.h"
@@ -22,28 +21,36 @@ class elem_filter: public arr<fs::path, fs::path> {
 };
 
 template<typename T>
-class comparator: public category::kleisli::arr<boost::shared_ptr<T>, file_type::compare_result> {
+class accumulator: public arr<boost::shared_ptr<T>, boost::shared_ptr<T> > {
     std::vector< boost::shared_ptr<T> > _values;
 public:
     void next(const boost::shared_ptr<T>& t) {
-        typedef typename std::vector<boost::shared_ptr<T> >::iterator iterator;
-        for (iterator it = _values.begin(); it != _values.end(); ++it) {
-            (*it)->compare(*t, sink<file_type::compare_result>::continuation());
-        }
         _values.push_back(t);
     }
+    void stop() {
+        if (_values.size() > 1) {
+            make_pair(_values.begin(), _values.end())
+            >>= sink< boost::shared_ptr<T> >::continuation();
+        }
+        _values.clear();
+    }
     boost::shared_ptr< end< boost::shared_ptr<T> > > clone() const {
-        return boost::make_shared< comparator<T> >(*this);
+        return boost::make_shared< accumulator<T> >(*this);
     }
 };
 
 void default_main(const program_options& po) {
+    struct : end< boost::shared_ptr<file_type::base> > {
+        void next(const boost::shared_ptr<file_type::base>& t) { std::cout << t->path() << "\n"; }
+        void stop() { std::cout << "\n"; }
+    } output;
+
     make_pair(po.input_files().begin(), po.input_files().end())
-    >>= The<fs::recursive>()
+    >>= fs::recursive()
     >>= (po.extensions().empty() ? The< arr<fs::path, fs::path> >() : The<elem_filter>(po.extensions()))
-    >>= The<file_typer_match_first>()
+    >>= file_typer_match_first()
     >>= clusterization<file_type::base>()
-    >>= The<comparator<file_type::base> >()
-    >>= The<iterator_end, file_type::compare_result>
-        (std::ostream_iterator<file_type::compare_result>(std::cout, "\n"));
+    >>= comparator<file_type::base, file_type::base>()
+    >>= accumulator<file_type::base>()
+    >>= output;
 }
diff --git a/trunk/src/file_types/base.cpp b/trunk/src/file_types/base.cpp
index 3af6390..514678c 100644
--- a/trunk/src/file_types/base.cpp
+++ b/trunk/src/file_types/base.cpp
@@ -13,29 +13,23 @@ boost::shared_ptr<base> base::try_file(const fs::path& file) {
     return boost::make_shared<base>(file);
 }
 
-void base::compare(const base& a, category::kleisli::end<compare_result>& cont) const {
-    if (fs::file_size(_path) != fs::file_size(a._path)) {
-        return;
+boost::shared_ptr<base> base::compare(const boost::shared_ptr<base>& a) const {
+    if (fs::file_size(_path) != fs::file_size(a->_path)) {
+        return boost::shared_ptr<base>();
     }
     const int buf_size = 4096;
     char buf1[buf_size], buf2[buf_size];
-    fs::ifstream file1(_path), file2(a._path);
+    fs::ifstream file1(_path), file2(a->_path);
     while (true) {
         file1.read(buf1, buf_size);
         file2.read(buf2, buf_size);
         if (file1.gcount() != file2.gcount() || file1.eof() != file2.eof() || memcmp(buf1, buf2, file1.gcount()) != 0) {
-            return;
+            return boost::shared_ptr<base>();
         }
         if (file1.eof() && file2.eof()) {
-            cont.next(compare_result(_path, a._path));
-            return;
+            return a;
         }
     }
 }
 
-std::ostream& operator<<(std::ostream& o, const compare_result& r) {
-    o << "files " << r.file1() << " and " << r.file2() << " are equal";
-    return o;
-}
-
 }
diff --git a/trunk/src/file_types/base.h b/trunk/src/file_types/base.h
index c440dd8..cbe563a 100644
--- a/trunk/src/file_types/base.h
+++ b/trunk/src/file_types/base.h
@@ -2,6 +2,7 @@
 #define _FILE_TYPE_BASE_H_
 
 #include <boost/shared_ptr.hpp>
+#include <vector>
 
 #include "../filesystem.h"
 #include "../type_list.h"
@@ -9,24 +10,13 @@
 
 namespace file_type {
 
-class compare_result {
-    const fs::path& _file1;
-    const fs::path& _file2;
-public:
-    compare_result(const fs::path& f1, const fs::path& f2): _file1(f1), _file2(f2) {}
-    const fs::path& file1() const { return _file1; }
-    const fs::path& file2() const { return _file2; }
-};
-
-std::ostream& operator<<(std::ostream& o, const compare_result& r);
-
 class base {
     fs::path _path;
 public:
     base(const fs::path& p): _path(p) {}
     const fs::path& path() const { return _path; }
     static boost::shared_ptr<base> try_file(const fs::path& file);
-    virtual void compare(const base& a, category::kleisli::end<compare_result>& cont) const;
+    virtual boost::shared_ptr<base> compare(const boost::shared_ptr<base>& a) const;
 };
 
 }
diff --git a/trunk/src/file_types/text.cpp b/trunk/src/file_types/text.cpp
index 746e15f..6992356 100644
--- a/trunk/src/file_types/text.cpp
+++ b/trunk/src/file_types/text.cpp
@@ -15,11 +15,11 @@ boost::shared_ptr<text> text::try_file(const boost::shared_ptr<base>& file) {
     return boost::shared_ptr<text>();
 }
 
-void text::compare(const base& a, category::kleisli::end<compare_result>& cont) const {
-    if (fs::file_size(path()) != fs::file_size(a.path())) {
-        return;
+boost::shared_ptr<base> text::compare(const boost::shared_ptr<base>& a) const {
+    if (fs::file_size(path()) != fs::file_size(a->path())) {
+        return boost::shared_ptr<base>();
     }
-    cont.next(compare_result(path(), a.path()));
+    return a;
 }
 
 }
diff --git a/trunk/src/file_types/text.h b/trunk/src/file_types/text.h
index a07ec13..44d2ed6 100644
--- a/trunk/src/file_types/text.h
+++ b/trunk/src/file_types/text.h
@@ -9,7 +9,7 @@ namespace file_type {
 struct text: base {
     text(const fs::path& p): base(p) {}
     static boost::shared_ptr<text> try_file(const boost::shared_ptr<base>& file);
-    void compare(const base& a, category::kleisli::end<compare_result>& cont) const;
+    boost::shared_ptr<base> compare(const boost::shared_ptr<base>& a) const;
 };
 
 }
diff --git a/trunk/src/kleisli.h b/trunk/src/kleisli.h
index f4c1929..69dd253 100644
--- a/trunk/src/kleisli.h
+++ b/trunk/src/kleisli.h
@@ -16,23 +16,27 @@ template<template<typename S, typename T, typename U> class R, typename S, typen
 template<typename S>
 struct end {
     virtual void next(const S&) = 0;
+    virtual void stop() = 0;
     virtual boost::shared_ptr< end<S> > clone() const { return boost::shared_ptr< end<S> >(); }
 };
 
 template<typename S>
 struct empty: end<S> {
     void next(const S&) {}
+    void stop() {}
     boost::shared_ptr< end<S> > clone() const { return boost::make_shared< empty<S> >(); }
 };
 
 template<typename V>
 void operator>>=(const V& from, end<V>& to) {
     to.next(from);
+    to.stop();
 }
 
 template<typename Iter, typename V>
 void operator>>=(const std::pair<Iter, Iter>& from, end<V>& to) {
     for (Iter it = from.first; it != from.second; to.next(*it++)) ;
+    to.stop();
 }
 
 template<typename Funct, typename V>
@@ -40,6 +44,7 @@ void operator>>=(const std::pair<Funct, int>& from, end<V>& to) {
     for (int i = 0; i < from.second; ++i) {
         to.next(from.first());
     }
+    to.stop();
 }
 
 template<typename T>
@@ -50,16 +55,13 @@ class sink {
     void set_continuation(end<T>& c) { _continuation = &c; }
 public:
     sink(): _continuation(&The< empty<T> >()) {}
-    void pass(const T& t) {
-        _continuation->next(t);
-    }
+    void pass(const T& t) { _continuation->next(t); }
 };
 
 template<typename S, typename T>
 struct arr: sink<T>, end<S> {
-    void next(const T& t) {
-        pass(t);
-    }
+    void next(const T& t) { pass(t); }
+    void stop() { sink<T>::continuation().stop(); }
     end<S>& operator>>=(end<T>& to) {
         set_continuation(to);
         return *this;
@@ -72,6 +74,7 @@ class iterator_end: public end<V> {
 public:
     iterator_end(const Iter& i): it(i) {}
     void next(const V& value) { *it++ = value; }
+    void stop() {}
     boost::shared_ptr< end<V> > clone() const { return boost::make_shared< iterator_end<V, Iter> >(it); }
 };