now `extract_head` should return the leftmost head directly, using its `abort_handler`:
let extract_head = \lst larger_computation. lst
- ; here's our f
(\hd sofar continue_handler abort_handler. abort_handler hd)
- ; here's our z
junk
- ; here's the continue_handler for the leftmost application of f
larger_computation
- ; here's the abort_handler
- larger_computation in
+ larger_computation
3. To extract tails efficiently, too, it'd be nice to fuse the apparatus developed
in these v5 lists with the ideas from the v4 lists, above.