* case or cond
@ 2009-10-10 10:03 Nordlöw
2009-10-11 17:22 ` Pascal J. Bourguignon
0 siblings, 1 reply; 3+ messages in thread
From: Nordlöw @ 2009-10-10 10:03 UTC (permalink / raw)
To: help-gnu-emacs
Is case more inefficient than cond?
Does it depend on what kinds of objects that are compared?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: case or cond
2009-10-10 10:03 case or cond Nordlöw
@ 2009-10-11 17:22 ` Pascal J. Bourguignon
0 siblings, 0 replies; 3+ messages in thread
From: Pascal J. Bourguignon @ 2009-10-11 17:22 UTC (permalink / raw)
To: help-gnu-emacs
Nordlöw <per.nordlow@gmail.com> writes:
> Is case more inefficient than cond?
>
> Does it depend on what kinds of objects that are compared?
Notice that case documentation says that:
Key values are compared by `eql'.
So:
(case expr
(v1 e1)
((v21 ... v2p) e2)
...
(otherwise eo))
is equivalent to:
(let ((e expr))
(cond
((eql e v1) e1)
((memq e '(v21 ... v2p)) e2)
...
(t eo)))
If your cond is not of that form, then it's hardly comparable to case.
On the other hand if it is, then indeed, case might be faster, because
it isn't necessarily implemented as a sequence of tests like cond.
--
__Pascal Bourguignon__
^ permalink raw reply [flat|nested] 3+ messages in thread
* case or cond
@ 2009-10-10 10:03 Nordlöw
0 siblings, 0 replies; 3+ messages in thread
From: Nordlöw @ 2009-10-10 10:03 UTC (permalink / raw)
To: help-gnu-emacs
Is case more inefficient than cond?
Does it depend on what kinds of objects that are compared?
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-10-10 10:03 case or cond Nordlöw
2009-10-11 17:22 ` Pascal J. Bourguignon
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2009-10-10 10:03 Nordlöw
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