[r6rs-discuss] Use backquote in "case"

From: Abdulaziz Ghuloum <aghuloum>
Date: Fri Nov 10 12:14:46 2006

On Nov 10, 2006, at 4:28 AM, Stanislav Ievlev wrote:

>> If "case" were defined in terms of backquote, though, this would be
>> possible:
>>
>> (define some-const 'xxx)
>>
>> (case some-val
>> [(,some-const)
>> ...])
> It's a too dangerous. We should avoid an implicit evaluation.

What implicit evaluation? The unquote here, just like the one in
quasiquote, is explicitly saying "evaluate this".
There might be other issues regarding when things are evaluated. For
example, are the following two expressions equivalent:
   (case e0 [(constant ,e1) e2] [else e3])
   (case e0 [(,e1 constant) e2] [else e3])

Aziz,,,
Received on Fri Nov 10 2006 - 12:14:27 UTC