exprarray.hpp

C++ Templates 完全导引范例

/* The following code example is taken from the book
 * "C++ Templates - The Complete Guide"
 * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
 *
 * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
 * 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 <stddef.h>
#include <cassert>
#include "sarray1.hpp"

template <typename T, typename Rep = SArray<T> >
class Array {
  private:
    Rep expr_rep;   // (access to) the data of the array

  public:
    // create array with initial size
    explicit Array (size_t s)
     : expr_rep(s) {
    }

    // create array from possible representation
    Array (Rep const& rb)
     : expr_rep(rb) {
    }

    // assignment operator for same type
    Array& operator= (Array const& b) { 
        assert(size()==b.size());
        for (size_t idx = 0; idx<b.size(); ++idx) {
            expr_rep[idx] = b[idx];
        }
        return *this;
    }

    // assignment operator for arrays of different type
    template<typename T2, typename Rep2>
    Array& operator= (Array<T2, Rep2> const& b) { 
        assert(size()==b.size());
        for (size_t idx = 0; idx<b.size(); ++idx) {
            expr_rep[idx] = b[idx];
        }
        return *this;
    }

    // size is size of represented data
    size_t size() const {
        return expr_rep.size();
    }

    // index operator for constants and variables
    T operator[] (size_t idx) const {
        assert(idx<size());
        return expr_rep[idx];
    }
    T& operator[] (size_t idx) {
        assert(idx<size());
        return expr_rep[idx];
    }

    // return what the array currently represents
    Rep const& rep() const {
        return expr_rep;
    }
    Rep& rep() {
        return expr_rep;
    }
};