C++ STL map::erase a non-existing key

c++ stl map key erase
fuad picture fuad · Mar 30, 2009 · Viewed 24.9k times · Source

Regarding the C++ STL map, erasing by key:-

 size_type map::erase ( const key_type& x );

Is it legal to erase a non-existing key? i.e. is the snippet below ok?

map<char,int> mymap;
mymap['c']=30;
mymap.erase('c');
mymap.erase('c');
mymap.erase('D');

Cheers

Answer

rlbond picture rlbond · Mar 30, 2009

Yes, in fact, std::map::erase() returns a size_type which indicates the number of keys erased. Thus it returns 0 for nothing erased and 1 for something erased for a map.

Related questions

What requirements must std::map key classes meet to be valid keys?

I want to map objects of a given class to objects of another. The class I want to use as key, however, was not written by me and is a simple struct with a few values. std::map orders it's …

Read More
Determine if map contains a value for a key?

What is the best way to determine if a STL map contains a value for a given key? #include <map> using namespace std; struct Bar { int i; }; int main() { map<int, Bar> m; Bar b = {0}; Bar …

Read More
How to check if std::map contains a key without doing insert?

The only way I have found to check for duplicates is by inserting and checking the std::pair.second for false, but the problem is that this still inserts something if the key is unused, whereas what I want is …

Read More