C++ Tutorial/template/define iterator operator
Define class with iterator support and direct element access
<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference" * by Nicolai M. Josuttis, Addison-Wesley, 1999 * * (C) Copyright Nicolai M. Josuttis 1999. * 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 <algorithm>
- include <functional>
- include <iostream>
- include <cstddef>
using namespace std;
/* PRINT_ELEMENTS()
* - prints optional C-string optcstr followed by * - all elements of the collection coll * - separated by spaces */
template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {
typename T::const_iterator pos; std::cout << optcstr; for (pos=coll.begin(); pos!=coll.end(); ++pos) { std::cout << *pos << " "; } std::cout << std::endl;
}
template<class T, std::size_t thesize> class carray {
private: T v[thesize]; // fixed-size array of elements of type T public: // type definitions typedef T value_type; typedef T* iterator; typedef const T* const_iterator; typedef T& reference; typedef const T& const_reference; typedef std::size_t size_type; typedef std::ptrdiff_t difference_type; // iterator support iterator begin() { return v; } const_iterator begin() const { return v; } iterator end() { return v+thesize; } const_iterator end() const { return v+thesize; } // direct element access reference operator[](std::size_t i) { return v[i]; } const_reference operator[](std::size_t i) const { return v[i]; } // size is constant size_type size() const { return thesize; } size_type max_size() const { return thesize; } // conversion to ordinary array T* as_array() { return v; }
}; int main() {
carray<int,10> a; for (unsigned i=0; i<a.size(); ++i) { a[i] = i+1; } PRINT_ELEMENTS(a); reverse(a.begin(),a.end()); PRINT_ELEMENTS(a); transform(a.begin(),a.end(), // source a.begin(), // destination negate<int>()); // operation PRINT_ELEMENTS(a);
}</source>
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