error: 'varName' was not declared in this scope [duplicate]

问题

I want to find the biggerst contour in my image (with opencv and C++). I have been read this thread: Finding Contours in OpenCV? and Draw the biggest element conncted using areaContours (OpenCV ) but I got error: 'varName' was not declared in this scope, which mean compiler think I haven't been declare that variable right? So this snippet of my code:

    threshold(Img, Img, t, 255, CV_THRESH_BINARY_INV);
    vector<vector<Point>> varName;
    findContours(Img, varName, CV_RETR_EXTERNAL, CV_CHAIN_APPROX_NONE);

I got this error:

   D:\OpencvWorkspace\....|50|error: 'varName' was not declared in this scope|

Line 50 is this code:

    vector<vector<Point>> varName;

My question. Why compiler ask this variable haven't declare at the line I declare that variable. could someone help me?

回答1:

You have used a pre c++11 standard compiler (as proven in your comment). The older standard had a problem letting the parser disambiguate a pair of closing angle brackets >> used in a nested template type specifier, from the operator>>(). Thus you had to write a space between them:

vector<vector<Point> > varName;
                 // ^ Note the space

回答2:

Yups like πάντα ῥεῖ say. the problem because space between ">" and ">". so I change the declaration from this:

   vector<vector<Point>> varName;

to this one:

   vector<vector<Point> > varName;

By adding space between ">" and ">" and the errror is gone.. Thanks πάντα ῥεῖ

来源：https://stackoverflow.com/questions/29329860/error-varname-was-not-declared-in-this-scope

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