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Subject: |
27.0.50; cl-loop: Calculate the array length just once |
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Date: |
Thu, 28 Dec 2017 01:10:29 +0900 |
X-Debbugs-CC: address@hidden
It looks sensible to calculate the array length just once,
instead of recalculate it on each iteration:
--8<-----------------------------cut here---------------start------------->8---
commit 1175db5cf09eb39e7e70703f38578d31b0dd9398
Author: Tino Calancha <address@hidden>
Date: Thu Dec 28 00:56:32 2017 +0900
cl-loop: Calculate the array length just once
* lisp/emacs-lisp/cl-macs.el (cl--parse-loop-clause):
Dont calculate the array length on each iteration (Bug#29866).
diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index f5311041cc..f671aea399 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -1317,11 +1317,13 @@ cl--parse-loop-clause
((memq word '(across across-ref))
(let ((temp-vec (make-symbol "--cl-vec--"))
+ (temp-len (make-symbol "--cl-len--"))
(temp-idx (make-symbol "--cl-idx--")))
(push (list temp-vec (pop cl--loop-args)) loop-for-bindings)
+ (push (list temp-len `(length ,temp-vec)) loop-for-bindings)
(push (list temp-idx -1) loop-for-bindings)
(push `(< (setq ,temp-idx (1+ ,temp-idx))
- (length ,temp-vec))
+ ,temp-len)
cl--loop-body)
(if (eq word 'across-ref)
(push (list var `(aref ,temp-vec ,temp-idx))
--8<-----------------------------cut here---------------end--------------->8---
In GNU Emacs 27.0.50 (build 32, x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
of 2017-12-28 built on calancha-pc
Repository revision: da94ea92bc3ba6c236b394c00e6bbb725131a149
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description: Debian GNU/Linux 9.3 (stretch)
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--- Begin Message ---
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Subject: |
Re: bug#29866: 27.0.50; cl-loop: Calculate the array length just once |
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Date: |
Mon, 08 Jan 2018 00:39:28 +0900 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Stefan Monnier <address@hidden> writes:
>> X-Debbugs-CC: address@hidden
>
> Thanks.
>
>> It looks sensible to calculate the array length just once,
>> instead of recalculate it on each iteration:
>
> I tend to agree, but I don't know very much about the intended semantics
> of Common Lisp's `loop` macro, nor about cl-loop's implementation (tho
> I admit I did mess with it without being really sure what I was doing).
Ok, let's do it.
Pushed to master branch as commit 'cl-loop: Calculate the array length just
once'
(bfca19e475c01f13dbacc7f8b7bb1aecf46cb7e4)
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