[plt-scheme] Syntax && SchemeQL

This has nothing to do with SrPersist. When you use ` (quasiquote)
then the , (unquote) must be physically nested inside. By the time
you macro expand, the cons structures have been formed from
quasiquote and unquote. -- Matthias


On May 20, 2004, at 2:33 PM, Ryan Culpepper wrote:

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> --- Toon Verwaest <camden at camden.be> wrote:
>> I'm trying out the SchemeQL, but it still seems to have a few
>> bugs...
>> One of the things I can't figure out how to fix it:
>>
>>   (define-syntax (add-constraint-to-table! stx)
>>       (syntax-case stx ()
>>             [(_ table . cons)]
>> 	    (syntax
>> 	    	(let  ((tab (quasiquote table))
>> 		       (con (quasiquote cons)))
>> 	  (if (table-definition? tab)
>> 	      (begin (set-table-definition-constraint!
>> 		      table
>> 		      (map format-table-named-constraint con))
>> 		     table)
>> 	      (raise-type-error 'add-check-to-table "table-definition
>> structure" tab))))]))
>>
>> When I call this, I can send stuff to the . cons part, with
>> unquote, but the table I can't unquote.
>>
>> I don't really know how the syntax-stuff works, but I would think
>> from the (quasiquote table),
>> that table should be able to have an unquote also..
>>
>> When I run it with unquote, it just says: not in quasiquote.
>
> I haven't examined the SchemeQL code, but this snippet looks like it
> should be using the local variable "tab" instead of the pattern
> variable "table" within the body of the let.
>
> Try replacing the code with this:
>
> (define-syntax (add-constraint-to-table! stx)
>   (syntax-case stx ()
>     [(_ table . cons)]
>      (syntax
>        (let  ((tab (quasiquote table))
>               (con (quasiquote cons)))
>          (if (table-definition? tab)
>              (begin (set-table-definition-constraint!
>                       tab ;; CHANGED!
>                       (map format-table-named-constraint con))
>                     tab) ;; CHANGED!
>              (raise-type-error 'add-check-to-table
>                                "table-definition structure"
>                                 tab))))]))
>
> Hope that helps,
> Ryan
>
>
>
> 	
> 		
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