branch: externals/dash
commit 578428abfe03c3c7d9c1ecc73d2f49747bb64cb4
Author: Paul Pogonyshev <pogonys...@gmail.com>
Commit: Matus Goljer <matus.gol...@gmail.com>
Add some implementation commentary to '-each-r'.
---
dash.el | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/dash.el b/dash.el
index 33cf56b..8d1d9a6 100644
--- a/dash.el
+++ b/dash.el
@@ -130,6 +130,11 @@ Return nil, used for side-effects only."
(declare (debug (form body))
(indent 1))
(let ((v (make-symbol "vector")))
+ ;; Implementation note: building vector is considerably faster
+ ;; than building a reversed list (vector takes less memory, so
+ ;; there is less GC), plus length comes naturally. In-place
+ ;; 'nreverse' would be faster still, but BODY would be able to see
+ ;; that, even if modification was reversed before we return.
`(let* ((,v (vconcat ,list))
(it-index (length ,v))
it)
