native `let rec` or `define`, then you can't use the fixed-point combinators
`Y` or <code>Θ</code>. Expressions using them will have non-terminating
reductions, with Scheme's eager/call-by-value strategy. There are other
- fixed-point combinators you can use with Scheme (in the [[week3]] notes they
+ fixed-point combinators you can use with Scheme (in the [week 3 notes](/week3/#index7h2) they
were <code>Y′</code> and <code>Θ′</code>. But even with
them, evaluation order still matters: for some (admittedly unusual)
evaluation strategies, expressions using them will also be non-terminating.
current list, the tail of the current list, and the result of continuing to
fold `f` over the tail, with a given base value `z`.
- Call this a **version 4** list. The empty list could be the same:
+ Call this a **version 4** list. The empty list can be the same as in v3:
- empty === \f z. z
+ <pre><code>empty ≡ \f z. z</code></pre>
The list constructor would be:
- make_list === \h t. \f z. f h t (t f z)
+ <pre><code>make_list ≡ \h t. \f z. f h t (t f z)</code></pre>
It differs from the version 3 `make_list` only in adding the extra argument
`t` to the new, outer application of `f`.