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- // (C) Copyright Jeremy Siek 2000-2004.
- // 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)
- #include <functional>
- #include <algorithm>
- #include <iostream>
- #include <boost/iterator/transform_iterator.hpp>
- // What a bummer. We can't use std::binder1st with transform iterator
- // because it does not have a default constructor. Here's a version
- // that does.
- namespace boost {
- template <class Operation>
- class binder1st {
- public:
- typedef typename Operation::result_type result_type;
- typedef typename Operation::second_argument_type argument_type;
- protected:
- Operation op;
- typename Operation::first_argument_type value;
- public:
- binder1st() { } // this had to be added!
- binder1st(const Operation& x,
- const typename Operation::first_argument_type& y)
- : op(x), value(y) {}
- typename Operation::result_type
- operator()(const typename Operation::second_argument_type& x) const {
- return op(value, x);
- }
- };
- template <class Operation, class T>
- inline binder1st<Operation> bind1st(const Operation& op, const T& x) {
- typedef typename Operation::first_argument_type arg1_type;
- return binder1st<Operation>(op, arg1_type(x));
- }
- } // namespace boost
- int
- main(int, char*[])
- {
- // This is a simple example of using the transform_iterators class to
- // generate iterators that multiply the value returned by dereferencing
- // the iterator. In this case we are multiplying by 2.
- // Would be cooler to use lambda library in this example.
- int x[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
- const int N = sizeof(x)/sizeof(int);
- typedef boost::binder1st< std::multiplies<int> > Function;
- typedef boost::transform_iterator<Function, int*> doubling_iterator;
- doubling_iterator i(x, boost::bind1st(std::multiplies<int>(), 2)),
- i_end(x + N, boost::bind1st(std::multiplies<int>(), 2));
- std::cout << "multiplying the array by 2:" << std::endl;
- while (i != i_end)
- std::cout << *i++ << " ";
- std::cout << std::endl;
- std::cout << "adding 4 to each element in the array:" << std::endl;
- std::copy(boost::make_transform_iterator(x, boost::bind1st(std::plus<int>(), 4)),
- boost::make_transform_iterator(x + N, boost::bind1st(std::plus<int>(), 4)),
- std::ostream_iterator<int>(std::cout, " "));
- std::cout << std::endl;
-
- return 0;
- }
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