Dictionary encoding strings to integers is a common compression technique. In GC'd languages it fakes out the garbage collector because your dictionary codes ar

Dictionary encoding strings to integers is a common compression technique. In GC'd languages it fakes out the garbage collector because your dictionary codes are essentially pointers but not actually pointers from the GC's perspective. You also have the benefit of potentially using a smaller integer than a pointer if you know roughly the number of values you're encoding beforehand.