[plt-scheme] [redex] matching question

Great, thanks Casey!

-- Éric


On Jun 4, 2010, at 2:48 PM, Casey Klein wrote:

> On Fri, Jun 4, 2010 at 1:14 PM, Eric Tanter <etanter at dcc.uchile.cl> wrote:
>> Hi,
>> 
>> I have a subtype? metafunction where one clause is as follows:
>> 
>> ((subtype? C_0 C_1 CT)
>>   #t
>>   (side-condition (not (equal? (term C_0) (term Object))))
>>   (where (C_0 C_2 any_1 any_2) (class-lookup C_0 CT))
>>   (side-condition (not (equal? (term C_0) (term C_1))))
>>   (side-condition (equal? (term C_2) (term C_1))))
>> 
>> ie. C_0 is subtype of C_1 if C_0 directly inherits from C_1
>> 
>> I find it redundant that I have to write the above, ie. introducing C_2 in the where clause to then check that C_2 and C_1 are equal.
>> 
>> At first I wrote:
>> 
>> ((subtype? C_0 C_1 CT)
>>   #t
>>   (side-condition (not (equal? (term C_0) (term Object))))
>>   (where (C_0 C_1 any_1 any_2) (class-lookup C_0 CT))
>>   (side-condition (not (equal? (term C_0) (term C_1)))))
>> 
>> putting C_1 directly in the pattern of the where clause, but it did not work (that is to say, it always matched, even if the superclass was different from C_1).
>> 
>> Can someone explain me why this is so?
>> 
> 
> John requested the same behavior a few months ago, and I agree it
> would be very handy.  I'll try to implement it in the next few weeks.