[plt-scheme] Please help test version 359.100

From: Jos Koot (jos.koot at telefonica.net)
Date: Tue Nov 14 06:36:50 EST 2006

----- Original Message ----- 
  From: Matthias Felleisen 
  To: Jacob Matthews 
  Cc: Robby Findler ; plt-scheme at list.cs.brown.edu 
  Sent: Tuesday, November 14, 2006 3:39 AM
  Subject: Re: [plt-scheme] Please help test version 359.100

  I don't think this is relevant. The true question is whether

    (+ (for-each add1 '()) (for-each sub1 '()))

  steps to

    (+ some-value some-value)

  or to

    (+ some-value some-different-value)

  I believe that the second one is the case already. -- Matthias

 Then why do I get: (eq? (for-each add1 '()) (for-each sub1 '())) --> #t ?
(version 359.100-svn4nov2006) Greetings, Jos Koot

  On Nov 13, 2006, at 6:52 PM, Jacob Matthews wrote:

  > On Nov 13, 2006, at 5:31 PM, Robby Findler wrote:
  >> Is "some object" allowed to be multiple values or not? That text
  >> suggests not.
  > "Types are associated with values (also called objects) rather than  
  > with variables" (section 1.1) seems to be the only definition of  
  > what an 'object' is. I think it's clear that they are saying that  
  > values are also called objects, and that by the normal rules of  
  > English we can conclude that the singular 'object' means the same  
  > thing as the singular 'value'. So the question becomes, are  
  > multiple values the same thing as a single value?  The report seems  
  > to think not (I'm going here by the descriptions of the values and  
  > call-with-values functions in section 6.4), though it plays its  
  > usual trick of simply not defining what happens if a context  
  > expects a single value and it receives multiple ones.
  > Applying this back to the original question, I think we have to  
  > conclude that for-each is supposed to be able to be called in  
  > contexts that expect exactly one value. In Schemes like PLT Scheme  
  > where contexts that expect one value signal an error if they  
  > receive some other number, then it's a violation of R5RS for for- 
  > each to behave the way 359.100 did; but for Schemes like Bigloo  
  > that have coercion rules that take a multi-value return to a single- 
  > value context, it's not a violation.
  > -jacob
  > (I actually wrote up a version of this before and then deleted it,  
  > thinking it was too technical for anybody to care about ... looks  
  > like I was wrong. :) )

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