[plt-scheme] Re: Scheme workshop survey

From: Jos Koot (jos.koot at telefonica.net)
Date: Sun Oct 19 17:44:52 EDT 2008

Is'nt this just a question about how to denote uses, quotations and 
The question was already asked and quite adequately dealt with about a 
century ago by W. V. Quine.
For Scheme the notation proposed in R5RS usually is satisfactory, I think.
But the notation can only be useful and rightly understood if we agree on 
For example I might say that <a> is not <a> because they occur on two 
different locations in the text. As a matter of fact they do, but <a> is a 
syntactical variable (or constants) referring to one and the very same thing 
whenever ocurring within the same scope.
Saying that <a> would not be the same as <a> would not be convenient 
(although it requires a common understanding of notation)

----- Original Message ----- 
From: "Matthias Felleisen" <matthias at ccs.neu.edu>
To: "Alan Watson" <alan at alan-watson.org>
Cc: "Shriram Krishnamurthi" <sk at cs.brown.edu>; "Scheme PLT" 
<plt-scheme at list.cs.brown.edu>
Sent: Sunday, October 19, 2008 10:20 PM
Subject: Re: [plt-scheme] Re: Scheme workshop survey

> Alan, you may also wish to read up on reduction semantics, e.g.,  Findler 
> and Matthews's appendix to the R6RS and their paper on R5RS.
> On Oct 19, 2008, at 3:57 PM, Alan Watson wrote:
>> The question at http://dynamo.iro.umontreal.ca/sw/survey/ has been 
>> changed.
>> The problem with regarding the (original) question as "what value  does 
>> it reduce to?" and the convention that we "consider values to  be a 
>> subset of expressions that do not require
>> further evaluation"  is that there is no standard means to write  such an 
>> expression that will be eqv? to the required expression.  Even Eli's 
>> answer doesn't get us there, as his expression produces  a value that 
>> will be equal? to the required value, but once again  not necessarily 
>> eqv?. That's why I say the original question is  unanswerable.
>> If the original question had been, "what is the value of (car '(a b  c)), 
>> we could regard 'a as a correct reply under these assumptions,  because 
>> the values of both expressions will be eqv?.
>> Now, this depends on interpreting "is" as meaning "eqv?" rather  than 
>> "equal?". However, one would not say that two different calls  to (list 
>> 'a 'b 'c) produced the same value (in Standard Scheme), so  I think eqv? 
>> is this correct predicate here.
>> Regards,
>> Alan
>> -- 
>> Alan Watson
>> http://www.alan-watson.org/
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