diff --git a/trunk/Makefile b/trunk/Makefile
index eebb820..ac22e68 100644
--- a/trunk/Makefile
+++ b/trunk/Makefile
@@ -1,25 +1,24 @@
-SRC_DIR = src
-PROJECT_NAME = pn
-SRCS = $(wildcard $(SRC_DIR)/*.cpp)
 LIBS = boost_program_options boost_filesystem boost_system
 CFLAGS = -O2 -Wall -pedantic
+PROJECT_NAME = pn
+SRC_DIR = src
+SRCS = $(wildcard $(SRC_DIR)/*.cpp)
+OBJS = $(patsubst $(SRC_DIR)/%.cpp,%.o,$(SRCS))
+
+builds = debug release
+debug_flags = -ggdb
+release_flags = -DNDEBUG
 
-.PHONY: first debug release makedirs clean
-first: debug
-debug:
-	@make makedirs DIR=debug
-	@make debug/$(PROJECT_NAME) DIR=debug FLAGS=-ggdb
-release:
-	@make makedirs DIR=release
-	@make release/$(PROJECT_NAME) DIR=release FLAGS=-DNDEBUG
-makedirs:
-	-@mkdir -p $(dir $(subst $(SRC_DIR),$(DIR),$(SRCS))) $(dir $(subst $(SRC_DIR),.depend,$(SRCS)))
+.PHONY: $(builds) clean
+$(builds): %: %-makedirs %/$(PROJECT_NAME)
+$(addsuffix -makedirs,$(builds)): %-makedirs:
+	-@mkdir -p $(dir $(subst $(SRC_DIR),$*,$(SRCS))) $(dir $(subst $(SRC_DIR),.depend,$(SRCS)))
 clean:
-	-@rm -rf debug release $(DIR) .depend
+	-@rm -rf $(builds) .depend
 
--include $(patsubst $(SRC_DIR)/%.cpp, .depend/%.dep, $(SRCS))
+-include $(patsubst $(SRC_DIR)/%.cpp,.depend/%.dep,$(SRCS))
 
-$(DIR)/$(PROJECT_NAME): $(patsubst $(SRC_DIR)/%.cpp, $(DIR)/%.o, $(SRCS))
-	g++ $^ -o $@ $(patsubst %,-l%,$(LIBS))
-$(DIR)/%.o: $(SRC_DIR)/%.cpp
-	g++ $< -c $(CFLAGS) -o $@ $(FLAGS) -MMD -MT $@ -MF .depend/$*.dep
+$(addsuffix /%.o,$(builds)): $(SRC_DIR)/%.cpp
+	g++ $< -c -o $@ $(CFLAGS) $($(D@)_flags) -MMD -MT $@ -MF .depend/$*.dep
+$(addsuffix /$(PROJECT_NAME),$(builds)): %$(PROJECT_NAME): $(addprefix %,$(OBJS))
+	g++ $^ -o $@ $(addprefix -l,$(LIBS))
diff --git a/trunk/src/filesystem.h b/trunk/src/filesystem.h
index 829b984..b6203fc 100644
--- a/trunk/src/filesystem.h
+++ b/trunk/src/filesystem.h
@@ -7,29 +7,26 @@
 
 #include "logger.h"
 #include "functor_iterator.h"
+#include "sequence.h"
 
 namespace fs {
 
 using namespace boost::filesystem;
 
-template<typename Funct>
-class recursive {
-    Funct _funct;
+class recursive: public seq<std::string, fs::path> {
 public:
-    typedef typename Funct::value_type value_type;
-    recursive(const Funct& funct): _funct(funct) {}
-    template<typename T>
-    void operator()(const T& value) {
+    void operator()(const fs::path& p) { put(p); }
+    void operator()(const std::string& value) {
         if (!exists(value)) {
             logger::std_stream() << value << " does not exists" << std::endl;
         } else
         if (is_directory(value)) {
             remove_copy_if(recursive_directory_iterator(value), recursive_directory_iterator(),
-                functor_iterator<Funct>(_funct),
+                functor_iterator<recursive, fs::path>(*this),
                 std::not1(std::ptr_fun((bool(*)(const path&))(&is_regular_file))));
         } else
         if (is_regular_file(value)) {
-            _funct(value);
+            put(value);
         } else {
             logger::std_stream() << value << " neither directory nor regular file" << std::endl;
         }
diff --git a/trunk/src/functor_iterator.h b/trunk/src/functor_iterator.h
index 0c95888..3c1bd7c 100644
--- a/trunk/src/functor_iterator.h
+++ b/trunk/src/functor_iterator.h
@@ -1,15 +1,12 @@
 #ifndef _FUNCTOR_ITERATOR_H_
 #define _FUNCTOR_ITERATOR_H_
 
-#include <vector>
-
-template<typename Funct>
+template<typename F, typename V>
 class functor_iterator {
-    Funct _funct;
+    F _funct;
 public:
-    typedef typename Funct::value_type value_type;
-    functor_iterator(const Funct& funct): _funct(funct) {}
-    functor_iterator& operator=(const value_type& elem) { _funct(elem); return *this; }
+    functor_iterator(const F& funct): _funct(funct) {}
+    functor_iterator& operator=(const V& elem) { _funct(elem); return *this; }
     functor_iterator& operator*() { return *this; }
     functor_iterator& operator++() { return *this; }
     functor_iterator operator++(int) { return *this; }
diff --git a/trunk/src/main.cpp b/trunk/src/main.cpp
index 2440eb7..59ce905 100644
--- a/trunk/src/main.cpp
+++ b/trunk/src/main.cpp
@@ -3,6 +3,16 @@
 #include "filesystem.h"
 #include "binary_functor.h"
 #include "comparer.h"
+#include "sequence.h"
+
+class HasExtension {
+    const std::vector<std::string>& _extensions;
+public:
+    HasExtension(const std::vector<std::string>& extensions): _extensions(extensions) { }
+    bool operator()(const fs::path& file) const {
+        return find(_extensions.begin(), _extensions.end(), file.extension()) != _extensions.end();
+    }
+};
 
 int main(int argc, char* argv[]) {
     stderr_logger std_logger(argv[0]);
@@ -10,8 +20,14 @@ int main(int argc, char* argv[]) {
     
     program_options po(argc, argv);
     
-    typedef std::ostream_iterator<comparer::result_type> out_iter;
-    typedef binary_functor<fs::path, out_iter, comparer> bin_funct;
-    for_each(po.input_files().begin(), po.input_files().end(),
-        fs::recursive<bin_funct>(bin_funct(out_iter(std::cout), comparer())));
+    make_pair(po.input_files().begin(), po.input_files().end())
+    >>= fs::recursive()
+    >>= po.extensions().empty()
+        ? (seq<fs::path, fs::path>&) The<id, fs::path>()
+        : The<filter, fs::path>(HasExtension(po.extensions()))
+    // >>= clusterize()
+    // >>= comparator()
+    >>= The<iterator_end, fs::path>(std::ostream_iterator<fs::path>(std::cout, "\n"));
+    
+    return 0;
 }
diff --git a/trunk/src/program_options.cpp b/trunk/src/program_options.cpp
index 4b7d8bc..1e15392 100644
--- a/trunk/src/program_options.cpp
+++ b/trunk/src/program_options.cpp
@@ -9,14 +9,16 @@ namespace po = boost::program_options;
 program_options::program_options(int argc, char* argv[]) {
     const std::string usage = std::string("Usage: ") + argv[0] + " [OPTIONS] FILES\n";
     try {
+        std::string extensions;
         po::options_description visible_options("Available options");
         visible_options.add_options()
+            ("extensions", po::value(&extensions), "Search through files with <extensions>")
             ("help", "Print this message and exit")
         ;
         
         po::options_description command_line_options;
         command_line_options.add(visible_options).add_options()
-            ("files", po::value< std::vector<std::string> >(&_input_files))
+            ("files", po::value(&_input_files))
         ;
         
         po::positional_options_description positional_options;
@@ -35,6 +37,17 @@ program_options::program_options(int argc, char* argv[]) {
             std::cout << visible_options << "\n";
             exit(0);
         }
+        
+        if (!extensions.empty()) {
+            for (size_t p = 0, p2 = 0; p2 != std::string::npos; p = p2 + 1) {
+                p2 = extensions.find(',', p);
+                std::string ext = extensions.substr(p, p2 != std::string::npos ? p2 - p : p2);
+                if (ext.length() > 0 && ext[0] != '.') {
+                    ext = "." + ext;
+                }
+                _extensions.push_back(ext);
+            }
+        }
     } catch(std::exception const& e) {
         logger::std(e.what());
         exit(1);
diff --git a/trunk/src/program_options.h b/trunk/src/program_options.h
index 9d37aaf..7686d65 100644
--- a/trunk/src/program_options.h
+++ b/trunk/src/program_options.h
@@ -8,9 +8,11 @@
 
 class program_options {
     std::vector<std::string> _input_files;
+    std::vector<std::string> _extensions;
 public:
     program_options(int argc, char* argv[]);
     const std::vector<std::string>& input_files() const { return _input_files; }
+    const std::vector<std::string>& extensions() const { return _extensions; }
 };
 
 #endif
diff --git a/trunk/src/sequence.h b/trunk/src/sequence.h
new file mode 100644
index 0000000..0b1861a
--- /dev/null
+++ b/trunk/src/sequence.h
@@ -0,0 +1,77 @@
+#ifndef _SEQUENCE_H_
+#define _SEQUENCE_H_
+
+template<typename S>
+struct end {
+    virtual void operator()(const S& v) = 0;
+};
+
+template<typename V>
+void operator>>=(const V& from, end<V>& to) {
+    to(from);
+}
+
+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(*it++)) ;
+}
+
+template<typename Funct, typename V>
+void operator>>=(const std::pair<Funct, int>& from, end<V>& to) {
+    for (int i = 0; i < from.second; ++i) {
+        to(from.first());
+    }
+}
+
+template<typename S, typename T>
+class seq: public end<S> {
+    end<T>* e;
+protected:
+    void put(const T& t) {
+        (*e)(t);
+    }
+public:
+    end<S>& operator>>=(end<T>& to) {
+        e = &to;
+        return *this;
+    }
+};
+
+template<typename V, typename Iter>
+class iterator_end: public end<V> {
+    Iter it;
+public:
+    iterator_end(const Iter& i): it(i) {}
+    void operator()(const V& value) { *it++ = value; }
+};
+
+template<typename T, typename P>
+class filter: public seq<T, T> {
+    P _p;
+public:
+    filter(const P& p): _p(p) {}
+    void operator()(const T& value) {
+        if (_p(value)) {
+            put(value);
+        }
+    }
+};
+
+template<typename T>
+struct id: seq<T, T> {
+    void operator()(const T& t) { put(t); }
+};
+
+template<typename T> T& The() { static T r; return r; }
+template<typename T> T& The(const T& t) { static T r(t); return r; }
+template<template<typename S> class R, typename S> R<S>& The() { static R<S> r; return r; }
+template<template<typename S> class R, typename S> R<S>& The(const S& s) { static R<S> r(s); return r; }
+template<template<typename S> class R, typename S> R<S>& The(const R<S>& t) { static R<S> r(t); return r; }
+template<template<typename S, typename T> class R, typename S, typename T> R<S, T>& The() { static R<S, T> r; return r; }
+template<template<typename S, typename T> class R, typename S, typename T> R<S, T>& The(const T& t) { static R<S, T> r(t); return r; }
+template<template<typename S, typename T> class R, typename S, typename T> R<S, T>& The(const R<S, T>& t) { static R<S, T> r(t); return r; }
+template<template<typename S, typename T, typename U> class R, typename S, typename T, typename U> R<S, T, U>& The() { static R<S, T, U> r; return r; }
+template<template<typename S, typename T, typename U> class R, typename S, typename T, typename U> R<S, T, U>& The(const U& u) { static R<S, T, U> r(u); return r; }
+template<template<typename S, typename T, typename U> class R, typename S, typename T, typename U> R<S, T, U>& The(const R<S, T, U>& t) { static R<S, T, U> r(t); return r; }
+
+#endif