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Re: What does "lacks a prefix" mean?
From: |
Pascal J. Bourguignon |
Subject: |
Re: What does "lacks a prefix" mean? |
Date: |
Fri, 10 Jul 2015 02:49:25 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
Drew Adams <drew.adams@oracle.com> writes:
>> > And non-parallelizable theoretically :)
>>
>> Regular let isn't parallelizable. It specifies that the value
>> expressions are evaluated in order.
>>
>> The only difference between the two is the environment within which
>> later expressions are evaluated.
>
> FWIW, Common Lisp specifies that "let performs the bindings
> in parallel and let* does them sequentially."
>
> That is theoretical, just a restatement that `let' bindings
> are independent. But it means that yes, they *could* be
> evaluated in parallel (because they are independent).
IF they are independent, and notably IF they are side effect free.
(let ((i 0))
(cons (let ((i 42)
(a (print (incf i)))
(b (print (incf i)))
(c (print (incf i))))
(list i a b c))
i))
prints:
1
2
3
--> ((42 1 2 3) . 3)
Here, there's now way the initialization expressions in the inner let
be evaluated in parallel. The left-to-right evaluation order is
imperative, because of the side effects.
--
__Pascal Bourguignon__ http://www.informatimago.com/
“The factory of the future will have only two employees, a man and a
dog. The man will be there to feed the dog. The dog will be there to
keep the man from touching the equipment.” -- Carl Bass CEO Autodesk
- Re: What does "lacks a prefix" mean?, (continued)
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/08
- Re: What does "lacks a prefix" mean?, Filipp Gunbin, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/09
- Re: What does "lacks a prefix" mean?, Stefan Monnier, 2015/07/10
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/11
- Message not available
- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/11
- Re: What does "lacks a prefix" mean?, Filipp Gunbin, 2015/07/13
- Message not available
- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/10
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- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/09
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/09
- Message not available
- Re: What does "lacks a prefix" mean?,
Pascal J. Bourguignon <=
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/10
- Message not available
- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/10
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/10
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- Re: What does "lacks a prefix" mean?, Barry Margolin, 2015/07/09
- Re: What does "lacks a prefix" mean?, Rusi, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/09
- Message not available
- Re: What does "lacks a prefix" mean?, Rusi, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/10
- RE: What does "lacks a prefix" mean?, Drew Adams, 2015/07/09
- Re: What does "lacks a prefix" mean?, Emanuel Berg, 2015/07/11