I think you're reading too much into the idea. If all memory is word-aligned, you only get 2 bits on a 32-bit machine and 3 bits on a 64-bit machine. If your pr

I think you're reading too much into the idea. If all memory is word-aligned, you only get 2 bits on a 32-bit machine and 3 bits on a 64-bit machine. If your property can't be encoded in 2 bits, it's probably not worth the trouble. OCaml uses the low bits to encode some basic type information for the GC. Pointers have both low bits 0, integers have the lowest bit set, and sum types have the lowest bit unset and the second bit set. This means integers are 31/63 bits long and using native-sized integers carries a significant performance penalty.