of the complex expression semantically depending only on this, not on that. A
demon evaluator who custom-picked the evaluation order to make things maximally
bad for you could ensure that all the semantically unnecessary computations got
-evaluated anyway. We don't have any way to prevent that. Later,
-we'll see ways to *semantically guarantee* one evaluation order rather than
-another. Though even then the demonic evaluation-order-chooser could make it
-take unnecessarily long to compute the semantically guaranteed result. Of
-course, in any real computing environment you'll know you're dealing with a
-fixed evaluation order and you'll be able to program efficiently around that.
+evaluated anyway. We don't yet know any way to prevent that. Later, we'll see
+ways to *guarantee* one evaluation order rather than another. Of
+course, in any real computing environment you'll know in advance that you're
+dealing with a fixed evaluation order and you'll be able to program efficiently
+around that.
In detail, then, here's what our v5 lists will look like:
>
> f a (f b (f c (f d (f e z))))
>
-> The left fold on the other hand starts combining `z` with elements from the left. `f z z` is then combined with `b`, and so on:
+> The left fold on the other hand starts combining `z` with elements from the left. `f z a` is then combined with `b`, and so on:
>
> f (f (f (f (f z a) b) c) d) e
>