dcsimg
Login | Register   
RSS Feed
Download our iPhone app
TODAY'S HEADLINES  |   ARTICLE ARCHIVE  |   FORUMS  |   TIP BANK
Browse DevX
Sign up for e-mail newsletters from DevX

By submitting your information, you agree that devx.com may send you DevX offers via email, phone and text message, as well as email offers about other products and services that DevX believes may be of interest to you. DevX will process your information in accordance with the Quinstreet Privacy Policy.


advertisement
 

Spruce Up Your Built-in Arrays-2 : Page 2


advertisement

WEBINAR:

On-Demand

Application Security Testing: An Integral Part of DevOps


Step 1: Array Wrapping
The following array_wrapper class template, originally presented by Bjarne Stroustrup, wraps a built-in array in a class that has no additional data members and therefore incurs no space overhead. Unlike ordinary STL containers, array_wrapper allocates its array statically on the stack, just as built-in arrays do. Most importantly, it provides the standard interface that other STL components recognize:

template <class T, int sz> struct array_wrapper { //uniform typedefs used in STL algorithms and containers typedef T value_type; typedef T* iterator; typedef const T * const_iterator; typedef T& reference; typedef const T& const_reference; T v[sz]; //the actual array; no other data members here // member functions of typical STL containers operator T* () {return v;} reference operator[] (size_t idx) {return v[idx];} const_reference operator[] (size_t idx) const {return v[idx];} iterator begin() {return v;} const_iterator begin() const {return v;} iterator end() {return v+sz;} const_iterator end() const {return v+sz;} size_t size() const {return sz;} };

This class is designed for utmost efficiency. It has neither a constructor nor a destructor. Additionally, all its member functions are inlined.

You initialize an array_wrapper as you would a built-in array. The resulting object can be used wherever a built-in array is expected:

void func(int *, int sz); // C function //wrap an array of 20 int's & initialize all members to 0 array_wrapper <int, 20> arr={0}; func(arr, arr.size()); //using T* conversion operator

Let's see how advantageous STL compatibility is. The following example uses the copy() algorithm and an ostream_iterator to display the contents of arr on the screen—as if it were an STL container:


copy(arr.begin(), arr.end(), ostream_iterator<int>(cout, " "));

The C++98 Standard Library doesn't define this class template. However, it will be added in the next revision round. In the meantime, you can download a similar class from Boost or roll your own.



Comment and Contribute

 

 

 

 

 


(Maximum characters: 1200). You have 1200 characters left.

 

 

Sitemap
Thanks for your registration, follow us on our social networks to keep up-to-date