問題描述
lỗi biểu thức lambda: biểu thức phải là giá trị có thể sửa đổi (lambda expression error: expression must be a modifiable lvalue)
Ok, the codes are:
vector<vector<double>> imageFiltered;
// some processing codes here
parallel_for( blocked_range<unsigned>(0, imageFiltered.size()),
[=](const blocked_range<unsigned>& r) {
for( unsigned i = r.begin(); i != r.end(); ++i ){
for( unsigned j = 0; j != imageFiltered[i].size(); ++j ) {
imageFiltered[i][j] = 0; // error here：expression must be a modifiable lvalue
}
}
});
And I've write another similar code block which works just fine. So, a little help here. PS: parallel_for is from Interl TBB.
參考解法
方法 1:
The [=] causes the lambda to capture by value, which means that it makes a copy of imageFiltered, and the copy is marked "const". Change the [=] to [&] to capture imageFiltered by reference, which should eliminate the problem.
(by Adrian Yu、Arch D. Robison)