Re: Modify STL map Object
Juha Nieminen <nospam@thanks.invalid> wrote:
Daniel T. <daniel_t@earthlink.net> wrote:
Juha Nieminen <nospam@thanks.invalid> wrote:
Daniel T. <daniel_t@earthlink.net> wrote:
There are several issues with your code, but in the interest of
brevity, I will concentrate on your question. map::insert only
inserts an object if it doesn't already exist. Otherwise, you
are expected to modify the object that is already in place.
That's why std::map::operator[] is so handy. It allows you to
insert a new key/value pair or, if a key already existed, to
modify the value, in one single statement. Eg:
myMap["hello"] = 5;
If a key with the value "hello" didn't exist, it will be inserted
and its value will be set to 5. If it existed, the existing value
will be changed to 5.
Just keep in mind, every time you use op[] you are doing a
logarithmic search
So do std::map::find() and std::map::insert(). So what?
Calling find once is better than calling op[] multiple times.
and in this case, if the element didn't already exist, the OP did
seem to want to add it so op[] would be inappropriate.
I don't understand. operator[] *does* add the element if it didn't
exist.
What if you don't want to add the element if it doesn't exist?
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