Lambda capture as const reference?

Question!

Is it possible to capture by const reference in a lambda expression?

I want the assignment marked below to fail, for example:

#include <cstdlib>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;

int main()
{
    string strings[] = 
    {
        "hello",
        "world"
    };
    static const size_t num_strings = sizeof(strings)/sizeof(strings[0]);

    string best_string = "foo";

    for_each( &strings[0], &strings[num_strings], [&best_string](const string& s)
      {
        best_string = s; // this should fail
      }
    );
    return 0;
}

Update: As this is an old question, it might be good to update it if there are facilities in C++14 to help with this. Do the extensions in C++14 allow us to capture a non-const object by const reference? (August 2015)



Answers

Use clang or wait until this gcc bug is fixed: bug 70385: Lambda capture by reference of const reference fails [https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70385]



This video can help you solving your question :)
By: admin