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libs/multi_index/example/non_default_ctor.cpp

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+/* Boost.MultiIndex example of use of multi_index_container::ctor_args_list.
+ *
+ * Copyright 2003-2008 Joaquin M Lopez Munoz.
+ * 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)
+ *
+ * See http://www.boost.org/libs/multi_index for library home page.
+ */
+
+#if !defined(NDEBUG)
+#define BOOST_MULTI_INDEX_ENABLE_INVARIANT_CHECKING
+#define BOOST_MULTI_INDEX_ENABLE_SAFE_MODE
+#endif
+
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/identity.hpp>
+#include <boost/multi_index/ordered_index.hpp>
+#include <algorithm>
+#include <iostream>
+#include <iterator>
+
+using boost::multi_index_container;
+using namespace boost::multi_index;
+
+/* modulo_less order numbers according to their division residual.
+ * For instance, if modulo==10 then 22 is less than 15 as 22%10==2 and
+ * 15%10==5.
+ */
+
+template<typename IntegralType>
+struct modulo_less
+{
+  modulo_less(IntegralType m):modulo(m){}
+
+  bool operator()(IntegralType x,IntegralType y)const
+  {
+    return (x%modulo)<(y%modulo);
+  }
+
+private:
+  IntegralType modulo;
+};
+
+/* multi_index_container of unsigned ints holding a "natural" index plus
+ * an ordering based on modulo_less.
+ */
+
+typedef multi_index_container<
+  unsigned int,
+  indexed_by<
+    ordered_unique<identity<unsigned int> >,
+    ordered_non_unique<identity<unsigned int>, modulo_less<unsigned int> >
+  >
+> modulo_indexed_set;
+
+int main()
+{
+  /* define a modulo_indexed_set with modulo==10 */
+
+  modulo_indexed_set::ctor_args_list args_list=
+    boost::make_tuple(
+      /* ctor_args for index #0 is default constructible */
+      nth_index<modulo_indexed_set,0>::type::ctor_args(),
+
+      /* first parm is key_from_value, second is our sought for key_compare */
+      boost::make_tuple(identity<unsigned int>(),modulo_less<unsigned int>(10))
+    );
+
+  modulo_indexed_set m(args_list);
+  /* this could have be written online without the args_list variable,
+   * left as it is for explanatory purposes. */
+
+  /* insert some numbers */
+
+  unsigned int       numbers[]={0,1,20,40,33,68,11,101,60,34,88,230,21,4,7,17};
+  const std::size_t  numbers_length(sizeof(numbers)/sizeof(numbers[0]));
+
+  m.insert(&numbers[0],&numbers[numbers_length]);
+
+  /* lists all numbers in order, along with their "equivalence class", that is,
+   * the equivalent numbers under modulo_less
+   */
+
+  for(modulo_indexed_set::iterator it=m.begin();it!=m.end();++it){
+    std::cout<<*it<<" -> ( ";
+
+    nth_index<modulo_indexed_set,1>::type::iterator it0,it1;
+    boost::tie(it0,it1)=get<1>(m).equal_range(*it);
+    std::copy(it0,it1,std::ostream_iterator<unsigned int>(std::cout," "));
+
+    std::cout<<")"<<std::endl;
+  }
+
+  return 0;
+}