[plt-scheme] Re: Scheme workshop survey

From: Richard Cleis (rcleis at me.com)
Date: Sun Oct 19 17:31:29 EDT 2008

Does the following progression make sense, by ordinary standards of  

(car '((a b c) x y z)) is '(a b c)

The value of (car '((a b c) x y z)) is (a b c)


On Oct 19, 2008, at 1:57 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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