-
* How shall we handle \[[∃x]]? As we said, GS&V really tell us how to interpret \[[∃xPx]], but for our purposes, what they say about this can be broken naturally into two pieces, such that we represent the update of our starting set `u` with \[[∃xPx]] as:
<pre><code>u >>= \[[∃x]] >>= \[[Px]]
<pre><code>bind_set (bind_set u \[[∃x]]) \[[Px]]
</code></pre>
-* Let's compare this to what \[[∃xPx]] would look like on a non-dynamic semantics, for example, where we use a simple reader monad to implement variable binding. Reminding ourselves, we'd be working in a framework like this. (Here we implement environments or assignments as functions from variables to entities, instead of as lists of pairs of variables and entities. An assignment `r` here is what `fun c -> List.assoc c r` would have been in [week6](
+* Let's compare this to what \[[∃xPx]] would look like on a non-dynamic semantics, for example, where we use a simple reader monad to implement variable binding. Reminding ourselves, we'd be working in a framework like this. (Here we implement environments or assignments as functions from variables to entities, instead of as lists of pairs of variables and entities. An assignment `r` here is what `fun c -> List.assoc c r` would have been in [week7](
/reader_monad_for_variable_binding).)
type assignment = char -> entity;;
That would be the meaning of \[[∃]], which we'd use like this:
- <pre><code>\[[∃]] \[[Q]]
+ <pre><code>\[[∃]] ( \[[Q]] )
</code></pre>
or this: