'((the . man) . (read . (the . ((side-effect . bad) . book))))
-and we said at the outset that the context `(the . (<> . book))` shouldn't need to know how to interact with affective meanings. That's precisely the problem we're trying to solve.
+and we said at the outset that the context `(the . (<> . book))` shouldn't need to know how to interact with affective meanings. (I'll use `<>` to indicate a "hole" in a larger expression.)
Let's use continuations
and then ask for the evaluation of:
- (+ 2 (three-thunk))
+ (+ (+ 2 (three-thunk)) 1)
you'll see something like:
<blockquote>
-<strong>"hi"</strong> 5
+<strong>"hi"</strong> 6
</blockquote>
-So the demonstration we tried in class was pedagogically flawed. It didn't properly display how continuations are a minimally effective apparatus for representing affective meaning. In fact, continuations were still doing the work, but it wasn't the explicit continuations we were writing out for you. It was instead continuations implicit in the `print` operation.
+In other words, the printing of "hi" already happens on the side, outside of the main evaluation. Continuations don't need to be explicitly invoked.
+
+So the demonstration we tried in class was pedagogically flawed. It didn't properly display how continuations are a minimally effective apparatus for representing affective meaning. In fact, continuations *were* still doing the work, but it wasn't the explicit continuations we were writing out for you. It was instead continuations implicit in the `print` operation.
So a better demonstration would do without any device like `print` that already incorporates continuations implicitly. Any continuation-manipulation should be fully explicit.
The idea here is we capture the continuation that the thunk `(damn)` has when it gets evaluated. This continuation is bound to the variable `k`. We supply `'id` as an argument to that continuation. When the main, at-issue tree is all built, then we return a pair `((side-effect bad) AT-ISSUE-TREE)`.
-However, this doesn't work. The reason is that an undelimited continuation represents the future of the evaluation of `(damn)` *until the end of the computation*. So when `'id` is supplied to `k`, we go back to building the at-issue tree until we're finished *and that's the end of the computation*. We never get to go back and evaluate the context `(cons (cons 'side-effect 'bad) <>)`.
+However, this doesn't work. The reason is that an undelimited continuation represents the future of the evaluation of `(damn)` *until the end of the computation*. So when `'id` is supplied to `k`, we go back to building the at-issue tree until we're finished *and that's the end of the computation*. We never get to go back and evaluate the application of `(cons (cons 'side-effect 'bad) <>)` to anything.
With undelimited continuations