Item 8. Using set and map

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Item 8. Using set and map

Difficulty: 5

In Item 7, we considered vector and deque . This time, the focus is on more news about the associative containers set, multiset, map , and multimap . ^[14]

^[14] Note that set and multiset aren't really "associative" in the usual sense of relating a lookup key with another value, the way a dictionary does. That's the job of map and multimap . But all four of these containers appear in the C++ standard under the heading "Associative Contain-ers," so I'll follow suit to be consistent.

1. 1. What's wrong with the following code? How would you correct it?

       map<int,string>::iterator i = m.find( 13 ); if( i != m.end() ) {   const_cast<int&>( i->first ) = 9999999; } 

   2. To what extent are the problems fixed by writing the following instead?

       map<int,string>::iterator i = m.find( 13 ); if( i != m.end() ) {   string s = i->second;   m.erase( i );   m.insert( make_pair( 9999999, s ) ); } 

2. Can you modify a set 's contents through a set::iterator ? Why or why not?

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