View Compilation Error

0_0_38223945_30747.cpp: In function 'ar2 encode(const string&)':
0_0_38223945_30747.cpp:40:14: error: expected unqualified-id before '[' token
         auto [r, c] = ctoi[s[i] - 'A'];
              ^
0_0_38223945_30747.cpp:42:13: error: 'r' was not declared in this scope
         ret[r] += t1[th[r][c]][i + 1];
             ^
0_0_38223945_30747.cpp:42:28: error: 'c' was not declared in this scope
         ret[r] += t1[th[r][c]][i + 1];
                            ^