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Re: [Scheme-reports] strange language in spec of `and' and `or'
- To: Andy Wingo <wingo@x>
- Subject: Re: [Scheme-reports] strange language in spec of `and' and `or'
- From: Alex Shinn <alexshinn@x>
- Date: Thu, 19 May 2011 09:51:04 -0700
- Cc: scheme-reports <scheme-reports@x>
- In-reply-to: <email@example.com>
- References: <firstname.lastname@example.org>
On Thu, May 19, 2011 at 8:55 AM, Andy Wingo <wingo@x> wrote:
> Section 4.2.1, p. 11, in the spec of `and':
> "The TEST expressions are evaluated from left to right, and the value
> of the first expression that evaluates to a false value (see section
> 6.3.1) is returned. Any remaining expressions are not evaluated. If
> all the expressions evaluate to true values, the value of the last
> expression is returned..."
> Why these weasel words? Is this to somehow permit implementations with
> more than one false value to return a false value from `and' which is
> not #f ?
Good point, that's possibly wording left over from
R4RS, where #f and '() were not necessarily distinct.
#f and '() could be distinct and yet there could be
other false values (as in Guile, no?), but I'm not
sure if we need to word the standard to accomodate
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