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Per Bothner skrev:
Consider Kent's implementation of cond in the reference implementation using the common extension: (define-syntax (cond x) (syntax-case x () [(_ c1 c2 ...)> ...[_ (syntax-error x)]))]))])) With define-syntax-case (at least if I understand you correctly) it becomes: (define-syntax-case cond () (x (syntax-case x () [(_ c1 c2 ...)> ... You could do that. But since syntax-error is not in the specification, I'm not sure it is relevant. If you leave out the syntax-error call, you get a worthwhile simplification: (define-syntax-case cond () ((_ c1 c2 ...) ...))
My point was that Refering to the original piece of syntax is often neccessary in order to give error messages in terms of user written syntax. so in that context it is relevant. I expect raise-syntax-error to be in the exception library. The lack of precise error reporting from syntax-rules macros has for me been the major reason to prefer syntax-case macros - even for small and otherwise simple macros. For that matter I'd like a portable way to work with source location information - including a read-syntax form that unlike read keeps the source location information.
Note also that if you *do* want syntax-error, it might be better to report error location more specifically that the entire cond.
For misuses like (cond) and (cond 1) it makes sense to report the entire macro call. -- Jens Axel Søgaard