Added new algorithm 'sort_subrange' from Sean Parent's CppCon keynote. Docs to come

include/boost/algorithm/sort_subrange.hpp

@@ -0,0 +1,72 @@
+/* 
+   Copyright (c) Marshall Clow 2008-2012.
+
+   Distributed under the Boost Software License, Version 1.0. (See accompanying
+   file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+ Revision history:
+   28 Sep 2015 mtc First version
+   
+*/
+
+/// \file sort_subrange.hpp
+/// \brief Sort a subrange
+/// \author Marshall Clow
+///
+/// Suggested by Sean Parent in his CppCon 2015 keynote
+
+#ifndef BOOST_ALGORITHM_SORT_SUBRANGE_HPP
+#define BOOST_ALGORITHM_SORT_SUBRANGE_HPP
+
+#include <functional>       // For std::less
+#include <iterator>         // For std::iterator_traits
+#include <algorithm>        // For nth_element and partial_sort
+
+#include <boost/range/begin.hpp>
+#include <boost/range/end.hpp>
+
+namespace boost { namespace algorithm {
+
+/// \fn sort_subrange ( T const& val, 
+///               Iterator first,     Iterator last, 
+///               Iterator sub_first, Iterator sub_last, 
+///               Pred p )
+/// \brief Sort the subrange [sub_first, sub_last) that is inside
+///     the range [first, last) as if you had sorted the entire range.
+/// 
+/// \param first       The start of the larger range
+/// \param last        The end of the larger range
+/// \param sub_first   The start of the sub range
+/// \param sub_last    The end of the sub range
+/// \param p           A predicate to use to compare the values.
+///                        p ( a, b ) returns a boolean.
+///
+  template<typename Iterator, typename Pred> 
+  void sort_subrange (
+  	Iterator first,     Iterator last, 
+  	Iterator sub_first, Iterator sub_last,
+  	Pred p)
+  {
+  	if (sub_first == sub_last) return; // the empty sub-range is already sorted.
+  	
+  	if (sub_first != first) { // sub-range is at the start, don't need to partition
+  		(void) std::nth_element(first, sub_first, last, p);
+  		++sub_first;
+  		}
+  	std::partial_sort(sub_first, sub_last, last, p);
+  }
+
+
+
+  template<typename Iterator> 
+  void sort_subrange (Iterator first, Iterator last, Iterator sub_first, Iterator sub_last)
+  {
+  	typedef typename std::iterator_traits<Iterator>::value_type value_type;
+  	return sort_subrange(first, last, sub_first, sub_last, std::less<value_type>());
+  }
+
+/// range versions?
+
+}}
+
+#endif // BOOST_ALGORITHM_SORT_SUBRANGE_HPP

test/Jamfile.v2

@@ -64,6 +64,9 @@ alias unit_test_framework
      [ run gather_test1.cpp unit_test_framework        : : : : gather_test1 ]
      [ compile-fail gather_fail1.cpp ]
 
+# SortSubrange tests
+     [ run sort_subrange_test.cpp unit_test_framework        : : : : sort_subrange_test ]
+
    ;
 }
 

test/sort_subrange_test.cpp

@@ -0,0 +1,137 @@
+#include <boost/config.hpp>
+#include <boost/algorithm/sort_subrange.hpp>
+#include <boost/algorithm/cxx11/is_sorted.hpp>
+
+#define BOOST_TEST_MAIN
+#include <boost/test/unit_test.hpp>
+
+#include <vector>
+#include <iostream>
+namespace ba = boost::algorithm;
+
+template <typename Iter>
+void check_sequence ( Iter first, Iter last, Iter sf, Iter sl )
+{
+	if (sf == sl) return;
+	for (Iter i = first; i < sf; ++i)
+		BOOST_CHECK(*i < *sf);
+	BOOST_CHECK(ba::is_sorted(sf, sl));
+	for (Iter i = sl; i < last; ++i)
+		BOOST_CHECK(*(sl-1) < *i);
+}
+
+template <typename Iter, typename Pred>
+void check_sequence ( Iter first, Iter last, Iter sf, Iter sl, Pred p )
+{
+	if (sf == sl) return;
+	for (Iter i = first; i < sf; ++i)
+		BOOST_CHECK(p(*i, *sf));
+	BOOST_CHECK(ba::is_sorted(sf, sl, p));
+	for (Iter i = sl; i < last; ++i)
+		BOOST_CHECK(p(*(sl-1), *i));
+
+}
+
+// 	for ( int i = 0; i < v.size(); ++i )
+// 		std::cout << v[i] << ' ';
+// 	std::cout << std::endl;
+
+
+BOOST_AUTO_TEST_CASE( test_main )
+{
+	{
+	std::vector<int> v;
+	for ( int i = 0; i < 10; ++i )
+		v.push_back(i);
+	
+	const std::vector<int>::iterator b = v.begin();
+	ba::sort_subrange(b, v.end(), b + 3, b + 6);
+	check_sequence   (b, v.end(), b + 3, b + 6);
+
+	BOOST_CHECK_EQUAL(v[3], 3);
+	BOOST_CHECK_EQUAL(v[4], 4);
+	BOOST_CHECK_EQUAL(v[5], 5);
+	
+//	Mix them up and try again - single element
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b + 7, b + 8);
+	check_sequence   (b, v.end(), b + 7, b + 8);
+
+	BOOST_CHECK_EQUAL(v[7], 7);
+
+//	Mix them up and try again - at the end
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b + 7, v.end());
+	check_sequence   (b, v.end(), b + 7, v.end());
+
+	BOOST_CHECK_EQUAL(v[7], 7);
+	BOOST_CHECK_EQUAL(v[8], 8);
+	BOOST_CHECK_EQUAL(v[9], 9);
+
+//	Mix them up and try again - at the beginning
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b, b + 2);
+	check_sequence   (b, v.end(), b, b + 2);
+
+	BOOST_CHECK_EQUAL(v[0], 0);
+	BOOST_CHECK_EQUAL(v[1], 1);
+
+//	Mix them up and try again - empty subrange
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b, b);
+	check_sequence   (b, v.end(), b, b);
+
+//	Mix them up and try again - entire subrange
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b, v.end());
+	check_sequence   (b, v.end(), b, v.end());
+	}
+
+	{
+	std::vector<int> v;
+	for ( int i = 0; i < 10; ++i )
+		v.push_back(i);
+	
+	const std::vector<int>::iterator b = v.begin();
+	ba::sort_subrange(b, v.end(), b + 3, b + 6, std::greater<int>());
+	check_sequence   (b, v.end(), b + 3, b + 6, std::greater<int>());
+
+	BOOST_CHECK_EQUAL(v[3], 6);
+	BOOST_CHECK_EQUAL(v[4], 5);
+	BOOST_CHECK_EQUAL(v[5], 4);
+
+//	Mix them up and try again - single element
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b + 7, b + 8, std::greater<int>());
+	check_sequence   (b, v.end(), b + 7, b + 8, std::greater<int>());
+
+	BOOST_CHECK_EQUAL(v[7], 2);
+
+//	Mix them up and try again - at the end
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b + 7, v.end(), std::greater<int>());
+	check_sequence   (b, v.end(), b + 7, v.end(), std::greater<int>());
+
+	BOOST_CHECK_EQUAL(v[7], 2);
+	BOOST_CHECK_EQUAL(v[8], 1);
+	BOOST_CHECK_EQUAL(v[9], 0);
+
+//	Mix them up and try again - at the beginning
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b, b + 2, std::greater<int>());
+	check_sequence   (b, v.end(), b, b + 2, std::greater<int>());
+
+	BOOST_CHECK_EQUAL(v[0], 9);
+	BOOST_CHECK_EQUAL(v[1], 8);
+
+//	Mix them up and try again - empty subrange
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b, b, std::greater<int>());
+	check_sequence   (b, v.end(), b, b, std::greater<int>());
+
+//	Mix them up and try again - entire subrange
+	std::random_shuffle(v.begin(), v.end());
+	ba::sort_subrange(b, v.end(), b, v.end(), std::greater<int>());
+	check_sequence   (b, v.end(), b, v.end(), std::greater<int>());
+	}
+}