Re: SETF for functions returning multiple values.

* "David McClain (as dbm at refined-audiometrics dot com)" <[email protected]> :
Wrote on Mon, 8 Jun 2026 11:13:44 -0700:
> I made my own digits become macro characters so that I can directly
> handle numbers written like these:
> +1Β°23’.23
> 2026/06/08T11:10:09U+7
> 520-234-3474
> and of course any number can be written with embedded comma or
> underscore: 1_234.5192_5542_112D0

Thanks, (I remember this as something I couldn't solve decades ago
when I tried to use the reader)

(comment to tfb below)

> I love it! Lisp no longer feels like a straightjacket to me. I can
> just directly type in the numbers as I need them.
>
> The only other time in my life where I had such freedom was in my
> ancient Forth Mount Control Systems on the world’s largest telescopes.
>
>> On Jun 8, 2026, at 11:02, Tim Bradshaw (as tfb at tfeb dot org)
>> <[email protected]> wrote:

>> (setf (values p1 p2) <form-returning-two-values>) should work when
>> p1 and p2 are places (the spec talks about this).

>> If F is a function returning two values, then you can't write a
>> (SETF F) function for it, but you can write a setf expansion pretty
>> easily.  So then you just can say (setf (f ...) (values v1 v2)).
>>
>> I don't think I've seen this done elsewhere.  Does it strike people
>> as reasonable?
>>
>> The reason I'm asking is that the delimited-string reading thing
>> I've been cleaning up now lets you control the closing delimiter, so
>> that for instance #D[foo/bar.ldat] might read as the contents of the
>> file foo/bar.ldat (ie the opening and closing delimiters are
>> different now, which they used not to be.
>>
>> The function which lets you set up handlers is get-dsr-handler and
>> it now returns two values the handler (or NIL) and the closing
>> delimiter (or NIL if it's the same as the opening delimiter).
>>
>> So I want to be able to say (setf (get-dsr-handler #\[) (values
>> my-handler #\])) say.

I'd just use a cons.  My cmucl-init has a read-verbatim-string reader
with this comment

```
(defvar *matching-delim-pairs* '((#\( . #\)) (#\{ . #\}) (#\[ . #\]))
    "Alist of (LDELIM . RDELIM) characters, for delimiting strings read by
VERBATIM-STRING-READER."))

  (setf (documentation 'verbatim-string-reader 'function) #$<reads
	$#X...X, where "..." is read verbatim. X, the first character read is
	treated as the delimiter. If *USE-MATCHING-DELIM-PAIRS-P* is non-NIL
	(default), look in the alist *MATCHING-DELIM-PAIRS* to find a matching
	delimiter, which is then used to terminate reading the string<))
```

(I think I had to set the documentation string in a separate form
because of I couldn't evaluate the (defun ...) form in emacs -- in
certain lisps -- if i put it inside the function)


>> [The actual hidden motivation for this is an utterly perverse usage
>> I thought of: you can make any digit character be an opening
>> delimiter and the closing delimiter for all of them be #\., and with
>> a suitable handler function
>>
>> ? #D1213,456,789.
>> 1213456789
>>
>> And even
>>
>>> #16DFFFF FF00 ABCD.
>> 281474959977421
>>
>> So that's pretty neat.]

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