c++: Search in a map without using an iterator

Question

Consider I have this:

std::map<int, int> intMap;
intMap[11] = 21; 
intMap[12] = 22; 
intMap[13] = 23; 
intMap[14] = 24; 

int val = 0; 

When I want to find the value of map[11], if exists, and put it into val I'm using:

std::map<int, int>::iterator it = intMap.find(11);
if(it != intMap.end())  
    val = it->second;

Is there a way of doing this without using an iterator? I mean, a shorter way.

int val = intMap[11] isn't an option for me since it adds 11 as a key to intMap if it wasn't there yet, something I'm not interested in. see here.

Answer 1

In c++11 map has a new method called at(Key) which will return a reference to the mapped value or throw an exception if the Key is not present at the map.

In c++ you will need to have an intermediary iterator.

Answer 2

André already mentions the new at() function. In other circumstances, the following might be useful:

template <typename Map, typename K, typename T>
T get(Map &map, const K &key, T def) {
    typename Map::const_iterator it = map.find(key);
    return (it == map.end() ? def : it->second);
}

Use it like:

int val = get(intMap, 11, 0);

You can also have a const version, with the advantage of returning a reference (the non-const version returns a value, because returning a reference to a default is rather limiting):

template <typename Map, typename K, typename T>
const T& get(const Map &map, const K &key, const T &def) {
    typename Map::const_iterator it = map.find(key);
    return (it == map.end() ? def : it->second);
}

Just for fun, this code is concise but it might lose for clarity. It does what you say in a comment below: nothing in the case where 11 is not in the map:

BOOST_FOREACH(const std::pair<int,int> &newval, intMap.equal_range(11)) {
    val = newval.second;
}