clarify extra-hidden-state-in-memory

diff --git a/ralf/_posts/2018-07-24-pointers-and-bytes.md b/ralf/_posts/2018-07-24-pointers-and-bytes.md
index dfd6bd1cfc1186d61cd74074ac9f84e6a5f47e08..5d6b60d492ec67b3a19bfd39bc1fd0ec5b96dbcd 100644 (file)
--- a/ralf/_posts/2018-07-24-pointers-and-bytes.md
+++ b/ralf/_posts/2018-07-24-pointers-and-bytes.md
@@ -162,7 +162,8 @@ We have to say what the value of `v` is, so we have to find some way to answer t
 (And this is an entirely separate issue from the problem with multiplication that came up in the last section. We just assume some abstract type `Pointer`.)
 
 We cannot represent a byte of a pointer as an element of `0..256`.
 (And this is an entirely separate issue from the problem with multiplication that came up in the last section. We just assume some abstract type `Pointer`.)
 
 We cannot represent a byte of a pointer as an element of `0..256`.

-Instead, we will remember both the pointer, and which byte of the pointer we got.
+Essentially, if we use a naive model of memory, the extra "hidden" part of a pointer (the one that makes it more than just an integer) would be lost whne a pointer is stored to memory and loaded again.
+We have to fix this, so we have to extend our notion of a "byte" to accomodate that extra state.

 So, a byte is now *either* an element of `0..256` ("raw bits"), *or* the n-th byte of some abstract pointer.
 If we were to implement our memory model in Rust, this might look as follows:
 {% highlight rust %}
 So, a byte is now *either* an element of `0..256` ("raw bits"), *or* the n-th byte of some abstract pointer.
 If we were to implement our memory model in Rust, this might look as follows:
 {% highlight rust %}