--- progress.hpp        2004-07-25 14:00:07.000000000 +0200
+++ /cygdrive/c/projects/boost/include/boost-1_33/boost/progress.hpp    2006-02-13 14:06:53.856875000 +0100
@@ -7,6 +7,8 @@
 //  See http://www.boost.org/libs/timer for documentation.
 
 //  Revision History
+//  13 Feb 06  Made it possible to customize output from progress_timer through
+//             user-supplied function object (Daniel Lidstrom).
 //   1 Dec 01  Add leading progress display strings (suggested by Toon Knapen)
 //  20 May 01  Introduce several static_casts<> to eliminate warning messages
 //             (Fixed by Beman, reported by Herve Bronnimann)
@@ -22,8 +24,10 @@
 #include <boost/timer.hpp>
 #include <boost/utility.hpp>  // for noncopyable
 #include <boost/cstdint.hpp>  // for uintmax_t
+#include <boost/function.hpp> // for function
 #include <iostream>           // for ostream, cout, etc
 #include <string>             // for string
+#include <sstream>            // for stringstream
 
 namespace boost {
 
@@ -36,9 +40,27 @@
 {
   
  public:
-  explicit progress_timer( std::ostream & os = std::cout )
+
+  // This is the default formatter. It shows the value with two decimals and appends " s".
+  struct default_si_formatter
+  {
+    std::string operator()(double s) const
+    {
+      // use istream instead of ios_base to workaround GNU problem (Greg Chicares)
+      std::stringstream stream;
+      stream.setf( std::istream::fixed, std::istream::floatfield );
+      stream.precision( 2 );
+      stream << s << " s" // "s" is System International d'Unités std
+             << std::endl;
+      return stream.str();
+    }
+  };
+
+  explicit progress_timer( std::ostream & os = std::cout,
+                           boost::function<std::string (double d)> formatter = default_si_formatter() )
      // os is hint; implementation may ignore, particularly in embedded systems
-     : m_os(os) {}
+     : m_os(os), m_formatter(formatter)
+  {}
   ~progress_timer()
   {
   //  A) Throwing an exception from a destructor is a Bad Thing.
@@ -47,14 +69,7 @@
   //  Therefore, wrap the I/O in a try block, catch and ignore all exceptions.
     try
     {
-      // use istream instead of ios_base to workaround GNU problem (Greg Chicares)
-      std::istream::fmtflags old_flags = m_os.setf( std::istream::fixed,
-                                                   std::istream::floatfield );
-      std::streamsize old_prec = m_os.precision( 2 );
-      m_os << elapsed() << " s\n" // "s" is System International d'Unités std
-                        << std::endl;
-      m_os.flags( old_flags );
-      m_os.precision( old_prec );
+       m_os << m_formatter(elapsed());
     }
 
     catch (...) {} // eat any exceptions
@@ -62,6 +77,7 @@
 
  private:
   std::ostream & m_os;
+  boost::function<std::string (double d)> m_formatter;
 };