Cannot Modify Non Const Member in Class

I try to modify one specific method in OpenCV. In the class definition;

class CV_EXPORTS CvANN_MLP : public CvStatModel
... 
protected
...
int activ_func;

when I try to modify activ_func field, I get:

error: assignment of data-member in read-only structure

error, however it is not defi开发者_开发问答ned as const, how is that possible?

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Unfortunately, you didn't give the context of the assignment statement itself. But I'm guessing that you're trying to assign to activ_func from a const member function.