branch: externals/dash
commit 75cde71040b91636f8c4a6c4d597fda775b8ce9e
Author: Wilfred Hughes <m...@wilfred.me.uk>
Commit: Wilfred Hughes <m...@wilfred.me.uk>
Ensure that -first-item is as fast as car
Add symbol properties to -first-item so the byte-compiler compiles
calls to the car opcode. This ensures that -first-item has the same
performance as car.
For example, given the following function:
(defun wh/call-first-item (x)
(-first-item x))
This would compile to:
byte code for wh/call-first-item:
args: (arg1)
0 constant -first-item
1 stack-ref 1
2 call 1
3 return
Whereas it now compiles to:
byte code for wh/call-first-item:
args: (arg1)
0 dup
1 car
2 return
---
dash.el | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/dash.el b/dash.el
index ce62b84..078175c 100644
--- a/dash.el
+++ b/dash.el
@@ -578,6 +578,11 @@ Alias: `-any'"
\(fn LIST)")
+;; Ensure that calls to `-first-item' are compiled to a single opcode,
+;; just like `car'.
+(put '-first-item 'byte-opcode 'byte-car)
+(put '-first-item 'byte-compile 'byte-compile-one-arg)
+
;; TODO: emacs23 support, when dropped remove the condition
(eval-when-compile
(require 'cl)
