From: Naoya Yamashita <conao3@gmail.com>
To: emacs-devel@gnu.org
Subject: [PATCH] * src/eval.c: Stop checking for nvars, and use only CONSP
Date: Tue, 02 Mar 2021 11:10:43 +0900 (JST) [thread overview]
Message-ID: <20210302.111043.609653289571449353.conao3@gmail.com> (raw)
[-- Attachment #1: Type: Text/Plain, Size: 802 bytes --]
Hi!
I found src/eval.c (let) has redundant conditions, that compares
the length of the list with the current index and also checks if
the current list is cons.
I remove latter check, and it compiled fine and passed all the
tests I added.
However, in such cases, Lisper prefers to compare that the
current list is cons, rather than comparing indices. Taking a
`cdr` and checking that it is cons is a Lisp idiom in situations
where `mapc` and `dolist` are not available.
The concern is it may be faster to check the index than CONSP.
This would be fast enough because CONSP in C is a macro, which is
eventually converted to a bitwise operation. The code is
considered to be easier to read and less prone to bugs than the
current code that includes variable reuse and reassignment.
Regards,
Naoya.
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From 622c96bdb41bda2727242f8a8078bb8114ef667f Mon Sep 17 00:00:00 2001
From: Naoya Yamashita <conao3@gmail.com>
Date: Tue, 2 Mar 2021 10:17:29 +0900
Subject: [PATCH] * src/eval.c: Stop checking for nvars, and use only CONSP
* src/eval.c (let): Remove checking nvars (length of arglist),
and use only CONSP check.
---
src/eval.c | 6 ++----
test/src/eval-tests.el | 27 +++++++++++++++++++++++++++
2 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/src/eval.c b/src/eval.c
index 542d7f686e..30783f204a 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -1001,11 +1001,10 @@ DEFUN ("let", Flet, Slet, 1, UNEVALLED, 0,
/* Make space to hold the values to give the bound variables. */
EMACS_INT varlist_len = list_length (varlist);
SAFE_ALLOCA_LISP (temps, varlist_len);
- ptrdiff_t nvars = varlist_len;
/* Compute the values and store them in `temps'. */
- for (argnum = 0; argnum < nvars && CONSP (varlist); argnum++)
+ for (argnum = 0; CONSP (varlist); argnum++)
{
maybe_quit ();
elt = XCAR (varlist);
@@ -1017,12 +1016,11 @@ DEFUN ("let", Flet, Slet, 1, UNEVALLED, 0,
else
temps[argnum] = eval_sub (Fcar (Fcdr (elt)));
}
- nvars = argnum;
lexenv = Vinternal_interpreter_environment;
varlist = XCAR (args);
- for (argnum = 0; argnum < nvars && CONSP (varlist); argnum++)
+ for (argnum = 0; CONSP (varlist); argnum++)
{
Lisp_Object var;
diff --git a/test/src/eval-tests.el b/test/src/eval-tests.el
index b2b7dfefda..3576254d7d 100644
--- a/test/src/eval-tests.el
+++ b/test/src/eval-tests.el
@@ -226,4 +226,31 @@ eval-tests/backtrace-in-batch-mode/demoted-errors
(should (equal (string-trim (buffer-string))
"Error: (error \"Boo\")")))))
+(ert-deftest eval-tests/let ()
+ (should (equal (let (a)
+ a)
+ nil))
+
+ (should (equal (let (a b)
+ (list a b))
+ '(nil nil)))
+
+ (should (equal (let ((a 1))
+ a)
+ 1))
+
+ (should (equal (let ((a 1) b)
+ (list a b))
+ '(1 nil)))
+
+ ;; (error "`let' bindings can have only one value-form" a 1 2)
+ (should-error (let ((a 1 2))
+ a)
+ :type 'error)
+
+ ;; (wrong-type-argument symbolp (a))
+ (should-error (let (((a) 1))
+ a)
+ :type 'wrong-type-argument))
+
;;; eval-tests.el ends here
--
2.30.1
next reply other threads:[~2021-03-02 2:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-02 2:10 Naoya Yamashita [this message]
2021-03-02 2:48 ` [PATCH] * src/eval.c: Stop checking for nvars, and use only CONSP Stefan Monnier
2021-03-02 3:09 ` Naoya Yamashita
2021-03-02 14:31 ` Stefan Monnier
2021-03-02 15:19 ` Pip Cet
2021-03-02 15:48 ` Stefan Monnier
2021-03-02 17:04 ` Pip Cet
2021-03-02 17:44 ` Stefan Monnier
2021-03-02 19:50 ` Pip Cet
2021-03-02 23:48 ` Stefan Monnier
2021-03-02 5:34 ` Pip Cet
2021-03-02 5:41 ` Eli Zaretskii
2021-03-02 7:14 ` Naoya Yamashita
2021-03-02 7:30 ` Pip Cet
2021-03-02 14:00 ` Eli Zaretskii
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