| // (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 std::unary_function<typename Operation::second_argument_type, |
| typename Operation::result_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; |
| } |
| |
| |