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.


Tip of the Day
Language: C++
Expertise: Beginner
Dec 16, 1999

WEBINAR:

On-Demand

Application Security Testing: An Integral Part of DevOps


Overload Operator []

Question:

Is it possible to overload the 'subscripting operator' [] so it will take char * as the index, similar to an array?

For example:

I want to write a class which will store 'name' and 'age'.

class_profile X

X["Mary"] = 18;
X["Mike"] = 20;
X["John"] = 12;

So it will work in such condition.

if ( X["John"] < 18 ) {
  cout << "Kid !" << endl;
}

Answer:

Actually, C++ already defined such a class, std::map<>. A map is also called an associative array, which is an array whose indices aren't necessarily integers. Thus, you can use a string as the subscript of an associative array.

std::map takes a pair of elements, one is the key and the second is the associated value. In your example, the key can be a string that contains a person name, and the associated value is the person's age. std::map overloads operator [] so you can do something like this:

#include  //for pair<>
#include 
#include 
#include 
using namespace std;
int main()
{
pair Person(string"Lee"),23); /*create a pair */

map mp; /*create a map*/

mp.insert(Person); /*insert pair into map*/

int age = mp["john"]; /*age = 23; string used as subscript */

return 0;
}

There are two steps here: first, you create a pair<> element using the standard class template std::pair (defined in ). The pair contains the name of the person and its associated value, namely the person's age. Then, you insert that pair into a map, and use map's subscript operator to retrieve the person's age by his or her name.

DevX Pro
 
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