empty [C++ Reference]
Keywords: stl,map,empty
Date: 2008-10-14T15:42:06-0700

[[empty]]
C++ Reference
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## empty

Syntax:

        #include <map>
        bool empty() const;

The empty() function returns true if the map has no elements, false otherwise.

For example, the following code uses empty() as the stopping condition on a while loop to clear a map and display its contents in order:

        struct strCmp {
          bool operator()( const char* s1, const char* s2 ) const {
            return strcmp( s1, s2 ) < 0;
          }
        };

        ...

        map<const char*, int, strCmp> ages;
        ages["Homer"] = 38;
        ages["Marge"] = 37;
        ages["Lisa"] = 8;
        ages["Maggie"] = 1;
        ages["Bart"] = 11;

        while( !ages.empty() ) {
          cout << "Erasing: " << (*ages.begin()).first << ", " << (*ages.begin()).second << endl;
          ages.erase( ages.begin() );
        }

When run, the above code displays:

        Erasing: Bart, 11
        Erasing: Homer, 38
        Erasing: Lisa, 8
        Erasing: Maggie, 1
        Erasing: Marge, 37

Related Topics: begin, erase, size

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