Sort command for sorting a map<int, double> by key?

[Claudius7]

Suppose I have a map m defined in this way:

m[7] = 0.3,
m[0] = 9.5,
m[3] = 2.

Now I want to sort this map by key, so that it will appear like

m[0] = 9.5,
m[3] = 2.,
m[7] = 0.3

Does it exist a sort command that does this? How to apply it?
Thanks in advance! :)

[gunnerfunner]

std::map<Key, Value> is sorted by less<Key> by default: http://www.cplusplus.com/reference/map/map/

and if you want to custom compare:
http://stackoverflow.com/questions/5733254/create-an-own-comparator-for-map

[Claudius7]

Thank you! So this is the also the reason why map iterators iterate through the key (rather than the values), is it so?

[gunnerfunner]

iterators iterate (traverse) the container across the container elements, so you could:

 
std::map<int,double>::const_iterator itr;
// to reach the key and value of any given map element 
itr->first; itr->second; 
//or 
(*itr).first; (*itr).second; 
//another alternative to reach the key/value of any std::map element would be to use range loops (c++11):
std::map<int,double> myMap;
for (const auto& elem : myMap)
{
	elem.first;//key
	elem.second;//value
}