How to implement the front() in C++

Hello, I am the student of the MscIT. I have learned the C++ language in the BscIT. But I can not know about the Header file functions. So, I would like to know about the front() function. I also would like to know about how can I able to implement the front() function in the C++ program and what can be the use of the front() function in the C++ language. Can anyone help me???

The front() function of the C++ language can be used for an access the next an element of the queue. The front() function can returns a address to the next an element in given specified the queue. That can be the oldest an element in the given specified queue and the similar an element that can be popped out from the given queue if member of the queue that is pop can be called.

The front() function can be used to display a address to the first an element at the front of the given specified queue of the C++ language. The following can be the general syntax of the front() function in the C++ language as :

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value_type& front ( );
const value_type& front ( ) const;

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The following code of lines can demonstrates you that how can you implement the front() function in the C++ language :

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#include <iostream>
#include <queue>
using namespace std;
int main ()
{
  queue<int> mque;
  mque.push(77);
  mque.push(16);
  mque.front() -= mque.back();   
  cout << "mque.front() is now " << mque.front() << endl;
  return 0;
}

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Output:

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mque.front() is now 61

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The front() function can be the member function that can an effectively calls the member with the similar name in the belonging class of an object. The front() function can returns a reference to the next element in the given specified queue. Member type value_type can be specified to the type of value that can be consisted by the underlying class, that can be the same as the first template parameter (S).

The front() function can produce the address to the first element of the given specified vector and that can execute in the constant time. For an example, the bellowed code that can uses a vector and the sort()_algorithm to view the first word that can be entered by a user in an alphabetical order :

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    vector<string> words;
    string str;
    while( cin >> str ) words.push_back(str);
    sort( words.begin(), words.end() );
    cout << "In alphabetical order, the first word is '" << words.front() << "'." << endl;

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When provided with this input:
now can the time for all good men to come to the aid of their country
…the above code displays:

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    In alphabetical order, the first word is 'aid'.

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