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Re: list versus apply

From: Marius Vollmer
Subject: Re: list versus apply
Date: Mon, 06 Jun 2005 00:11:35 +0300
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.0.50 (gnu/linux)

Kevin Ryde <address@hidden> writes:

> Marius Vollmer <address@hidden> writes:
>>   (define (list . args) args)
>> is an acceptable definition of list.  Is it not?
> Yep, because args is of course a fresh list when calling a lambda, but
> it looks like primitives (C code) aren't called with a copied list
> like that.

Ahh, I see.  R5RS says: "The value stored in the binding of the last
variable will be a newly allocated list of the actual arguments..."  I
think I was confusing this with Common Lisp, which says: "The value of
a rest parameter is permitted, but not required, to share structure
with the last argument to apply."

> (I guess having primitives like that makes some sense, only a few are
> interested in modifying or re-using their input "rest" list.)

We need to document this difference between Scheme functions and C
primitives, I'd say.

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