how to initialize associate data in map?

[forrestarrow]

Hi everyone,
I used STL map in my code and I am wondering is the associate data automatically initialized or not. The reason I am asking is that I have two arrays of data, and the first array is index, and second array is my data corresponding to the index. But there are duplicate indexs and I want to add up the data of duplicate index.

For example;
map<int index, double data> mid;
mid[index] += data;

So I want to know at beginning, is the data are initialized to 0. or I have to do it myself? Thanks in advance.

Jingbin

[gpraghuram]

Hi everyone,
I used STL map in my code and I am wondering is the associate data automatically initialized or not. The reason I am asking is that I have two arrays of data, and the first array is index, and second array is my data corresponding to the index. But there are duplicate indexs and I want to add up the data of duplicate index.

For example;
map<int index, double data> mid;
mid[index] += data;

So I want to know at beginning, is the data are initialized to 0. or I have to do it myself? Thanks in advance.

Jingbin

mpas dosent allow duplicate indexes, only multi-map allow duplicate index.

Raghu

[keerthiramanarayan]

The map in your case will be initialized to 0.00 . However it is not the case with types such as strings or user classes. which tend to by null(0). So you should be careful.