diff --git a/example/transform_iterator_example.cpp b/example/transform_iterator_example.cpp new file mode 100644 index 0000000..4733997 --- /dev/null +++ b/example/transform_iterator_example.cpp @@ -0,0 +1,78 @@ +// (C) Copyright Jeremy Siek 2000-2004. +// Permission to copy, use, modify, sell and distribute this software +// is granted provided this copyright notice appears in all +// copies. This software is provided "as is" without express or +// implied warranty, and with no claim as to its suitability for any +// purpose. + + +#include +#include +#include +#include + +// 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 binder1st + : public std::unary_function { + 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 + inline binder1st bind1st(const Operation& op, const T& x) { + typedef typename Operation::first_argument_type arg1_type; + return binder1st(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 > Function; + typedef boost::transform_iterator doubling_iterator; + + doubling_iterator i(x, boost::bind1st(std::multiplies(), 2)), + i_end(x + N, boost::bind1st(std::multiplies(), 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(), 4)), + boost::make_transform_iterator(x + N, boost::bind1st(std::plus(), 4)), + std::ostream_iterator(std::cout, " ")); + std::cout << std::endl; + + return 0; +} + +