Re: unordered_map non-existent key
On 22 Jul., 01:30, Helmut Jarausch <jarau...@igpm.rwth-aachen.de>
wrote:
Hi,
what happens if I try to access a non-existent key by using
operator[] ?
e.g.
#include <unordered_map>
typedef std::unordered_map<int,int> IntHash;
typedef IntHash::value_type ValuePair;
int main() {
IntHash H;
H.insert(ValuePair(3,9));
int v = H[7];
cout << v << endl;
}
gcc-4.4.4 does not throw an exception and returns 0.
What should it do? Throwing an exception or returning a
default value (if this, how to set the default value)?
This member function is similarly specified as
the corresponding operator[] of std::[multi]map:
If not found, a value-initialized (aka default-
constructed) key will be inserted.
There is no way to specify a different default
key. If you prefer an exception, you should
use the new member function at(), which throws
std::out_of_range if no such element is present.
HTH & Greetings from Bremen,
Daniel Kr?gler
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