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Re: (+ (values 1 2)) should be 1
From: |
Hans Aberg |
Subject: |
Re: (+ (values 1 2)) should be 1 |
Date: |
Tue, 24 May 2011 15:48:32 +0200 |
On 24 May 2011, at 15:11, Andy Wingo wrote:
>>>>> But, it is 1 and 2, currently. (+ FOO) inlines just to FOO, too
>>>>> optimistically.
>>>>
>>>> It is unspecified according to rsr5.
>>>
>>> I know. I'm talking about Guile here.
>>
>> The Guile manual, sec. 10.2.5.2, says that SCM_UNSPECIFIED is to be used
>> when the Scheme standard says the return is an unspecified value.
>>
>> So this Lisp extension breaks off from that. If one wants it, perhaps, there
>> should be some way to invoke it.
>
> Hans, you are misreading. (+ 1) is 1 according to the R5RS. (+ "foo")
> is an error. (+ (values 1 2)) is unspecified, as an instance of
> returning an unexpected number of values to a continuation, but it is
> not an instance of the unspecified value.
Andy, I think (values 1 2) should here return SCM_UNSPECIFIED first argument to
'+', so that people will know that the standard does leave the value
unspecified.
> When a continuation that expects one value receives more values than it
> is expecting -- e.g., the <> in (+ <>) expects one value -- Guile
> truncates those values to the first one. If such a continuation
> receives 0 values, Guile signals an error.
So here I think one should enable some kind of Lisp-extension to get that.
There is no guarantee that Guile will not change again unless doing something
like that. So it is useless for regular programming.
Hans
- (+ (values 1 2)) should be 1, Andy Wingo, 2011/05/22
- Re: (+ (values 1 2)) should be 1, Hans Aberg, 2011/05/23
- Re: (+ (values 1 2)) should be 1, Andy Wingo, 2011/05/23
- Re: (+ (values 1 2)) should be 1, Hans Aberg, 2011/05/23
- Re: (+ (values 1 2)) should be 1, Hans Aberg, 2011/05/24
- Re: (+ (values 1 2)) should be 1, Andy Wingo, 2011/05/24
- Re: (+ (values 1 2)) should be 1,
Hans Aberg <=
- Re: (+ (values 1 2)) should be 1, Andy Wingo, 2011/05/24
- Re: (+ (values 1 2)) should be 1, Hans Aberg, 2011/05/24
- Re: (+ (values 1 2)) should be 1, Mark H Weaver, 2011/05/24
- Re: (+ (values 1 2)) should be 1, Hans Aberg, 2011/05/25
- Re: (+ (values 1 2)) should be 1, Mark H Weaver, 2011/05/25
- Re: (+ (values 1 2)) should be 1, Hans Aberg, 2011/05/25