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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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