Patch by Riccardo Marcangelo: Added a pop_back() member function which decreases the size of the bitset by one

bitset_test.hpp

@@ -2,6 +2,7 @@
 //              Copyright (c) 2001 Jeremy Siek
 //        Copyright (c) 2003-2006, 2008 Gennaro Prota
 //             Copyright (c) 2014 Ahmed Charles
+//            Copyright (c) 2014 Riccardo Marcangelo 
 //
 // Distributed under the Boost Software License, Version 1.0.
 //    (See accompanying file LICENSE_1_0.txt or copy at
@@ -367,6 +368,20 @@ struct bitset_test {
     BOOST_CHECK(b.size() == 0);
   }
 
+  static void pop_back(const Bitset& lhs)
+  {
+    Bitset b(lhs);
+    b.pop_back();
+    BOOST_CHECK(b.size() == lhs.size() - 1);
+    for (std::size_t i = 0; i < b.size(); ++i)
+      BOOST_CHECK(b[i] == lhs[i]);
+
+    b.pop_back();
+    BOOST_CHECK(b.size() == lhs.size() - 2);
+    for (std::size_t j = 0; j < b.size(); ++j)
+      BOOST_CHECK(b[j] == lhs[j]);
+  }
+
   static void append_bit(const Bitset& lhs)
   {
     Bitset b(lhs);

dyn_bitset_unit_tests1.cpp

@@ -2,6 +2,7 @@
 //              Copyright (c) 2001 Jeremy Siek
 //           Copyright (c) 2003-2006 Gennaro Prota
 //             Copyright (c) 2014 Ahmed Charles
+//            Copyright (c) 2014 Riccardo Marcangelo 
 //
 // Copyright (c) 2014 Glen Joseph Fernandes
 // glenfe at live dot com
@@ -379,6 +380,25 @@ void run_test_cases( BOOST_EXPLICIT_TEMPLATE_TYPE(Block) )
     Tests::clear(a);
   }
   //=====================================================================
+  // Test pop back 
+  {
+    boost::dynamic_bitset<Block> a(std::string("01"));
+    Tests::pop_back(a);
+  }
+  {
+    boost::dynamic_bitset<Block> a(std::string("10"));
+    Tests::pop_back(a);
+  }
+  {
+    const int size_to_fill_all_blocks = 4 * bits_per_block;
+    boost::dynamic_bitset<Block> a(size_to_fill_all_blocks, 255ul);
+    Tests::pop_back(a);
+  }
+  {
+    boost::dynamic_bitset<Block> a(long_string);
+    Tests::pop_back(a);
+  }
+  //=====================================================================
   // Test append bit
   {
     boost::dynamic_bitset<Block> a;

dynamic_bitset.html

@@ -180,6 +180,7 @@ public:
     void <a href=
 "#resize">resize</a>(size_type num_bits, bool value = false);
     void <a href="#clear">clear</a>();
+    void <a href="#pop_back">pop_back</a>();
     void <a href="#push_back">push_back</a>(bool bit);
     void <a href="#append1">append</a>(Block block);
 
@@ -834,6 +835,15 @@ void <a id="clear">clear</a>()
 <b>Effects:</b> The size of the bitset becomes zero.<br />
  <b>Throws:</b> nothing.
 
+<hr />
+<pre>
+void <a id="pop_back">pop_back</a>();
+</pre>
+
+<b>Precondition:</b> <tt>!this-&gt;empty()</tt>.<br />
+<b>Effects:</b> Decreases the size of the bitset by one.<br />
+ <b>Throws:</b> nothing.
+ 
 <hr />
 <pre>
 void <a id="push_back">push_back</a>(bool value);

include/boost/dynamic_bitset/dynamic_bitset.hpp

@@ -6,6 +6,7 @@
 //
 // Copyright (c) 2014 Glen Joseph Fernandes
 // glenfe at live dot com
+// Copyright (c) 2014 Riccardo Marcangelo
 //
 // Distributed under the Boost Software License, Version 1.0.
 //    (See accompanying file LICENSE_1_0.txt or copy at
@@ -227,6 +228,7 @@ public:
     void resize(size_type num_bits, bool value = false);
     void clear();
     void push_back(bool bit);
+    void pop_back();
     void append(Block block);
 
     template <typename BlockInputIterator>
@@ -746,6 +748,22 @@ push_back(bool bit)
   set(sz, bit);
 }
 
+template <typename Block, typename Allocator>
+void dynamic_bitset<Block, Allocator>::
+pop_back() 
+{
+  const size_type old_num_blocks = num_blocks();
+  const size_type required_blocks = calc_num_blocks(m_num_bits - 1);
+  
+  if (required_blocks != old_num_blocks) {
+    m_bits.pop_back(); 
+  }
+    
+  --m_num_bits;
+  m_zero_unused_bits();
+}
+
+
 template <typename Block, typename Allocator>
 void dynamic_bitset<Block, Allocator>::
 append(Block value) // strong guarantee