Chapter 22 of Practical Common Lisp explains (among other things) how to use both the keys and the values when iterating through a hash table with the loop macro:
(loop for k being the hash-keys in h using (hash-value v) ...)
The explanation is concluded with the following footnote:
Don't ask me why
LOOP's authors chickened out on the no-parentheses style for theusingsubclause.
That's perfectly fine for the book and I don't blame Peter Seibel for not knowing it. Still, I am somewhat curious about the reasons for this design decision of. Why isn't the syntax something like
(loop for k being the hash-keys in h using hash-value v ...)
Is it easier to parse? Or is there some deeper reason behind it?