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This chapter is from the book

This chapter is from the book

Operations Common to All Containers

The following operations are common to all the container classes (as well as the string class):

  • The equality (==) and inequality (!=) operators return true or false.

  • The assignment (=) operator copies one container into another.

  • empty() returns true if the container holds no elements.

  • size() returns a count of the elements currently held within the container.

  • clear() deletes all the elements.

  • The following function exercises each of these operations:

    void comp( vector<int> &v1, vector<int> &v2 )
    {
       // are the two vectors equal?
       if ( v1 == v2 ) 
          return;
       // is either vector empty?
       if ( v1.empty() || v2.empty() ) return;
    
       // no point defining it unless we are going to use it!
       vector<int> t;
    
       // assign t the largest vector
       t = v1.size() > v2.size() ? v1 : v2;
    
       // ... use t ...
    
       // ok. empty t of its elements
       // t.empty() will now return true
       // t.size() will now return 0
       t.clear();
    
       // ... ok, fill up t and use it some more ...
    }

    Each container supports a begin() and an end() operation to return, respectively, an iterator to the first element of the container and 1 past the last valid element:

    • begin() returns an iterator to the first element.

    • end() returns an iterator that addresses 1 past the last element.

    Typically, we iterate across a container starting at begin() and stopping when we reach end(). All containers support an insert() operation to add elements and an erase() operation to delete elements.

    • insert() adds one element or a range of elements to a container.

    • erase() deletes one element or a range of elements from a container.

    The behavior of insert() and erase() varies depending on whether the container is sequential or associative. Sequential containers are discussed in the next section.

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