GNU bug report logs - #69919
Inaccurate api-procedures manual sentence on lambda formal arguments

Previous Next

To reply to this bug, email your comments to 69919 AT debbugs.gnu.org.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Richard Sent <richard <at> freakingpenguin.com>
To: bug-guile <at> gnu.org
Subject: Inaccurate api-procedures manual sentence on lambda formal arguments
Date: Wed, 20 Mar 2024 13:40:58 -0400

Hi Guile,

I noticed the following line in the manual on (lambda) in (info "(guile)
Lambda"). Emphasis in **.

> -- syntax: lambda formals body
>     ...
>     ‘(VARIABLE1 ... VARIABLEN . VARIABLEN+1)’
>          If a space-delimited period precedes the last variable, then
>          the procedure takes N or more variables where N is the number
>          of formal arguments before the period.  *There must be at
>          least one argument before the period.*

That would mean a procedure like

--8<---------------cut here---------------start------------->8---
((lambda ( . args)
  args) 1) ;=>(1) runs fine in 3.0.9
--8<---------------cut here---------------end--------------->8---

is invalid because there isn't an argument before the period. I've
encountered Guile code that relies on this behavior before, even in the
Guile repo. For example, in guile/benchmark/measure.scm:

--8<---------------cut here---------------start------------->8---
(define (measure . args)
 ...)
;; should be identical to
(define measure (lambda ( . args) ...))
--8<---------------cut here---------------end--------------->8---

Ergo, I think the sentence

> There must be at least one argument before the period

should be removed. This line seems to be from the R5RS standard [1], but
this sentence is in api-procedures.texi, not the R5RS manual, so I
assume it should reflect Guile's implementation.

[1] https://conservatory.scheme.org/schemers/Documents/Standards/R5RS/HTML/r5rs-Z-H-2.html#%_toc_%_sec_4.1.4

-- 
Take it easy,
Richard Sent
Making my computer weirder one commit at a time.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.