Re: Simplified slot access in goops

[Clinton Ebadi <clinton@unknownlamer.org>]

"Panicz Maciej Godek" <godek.maciek@gmail.com> writes:

>> with-slots uses symbol-macrolet[0] to bind each of the variable names to
>> symbol macros within its body. I don't know of anything in Guile that is
>> equivalent.
>
> R5RS pattern language allows to create syntactic aliases for practically
> any form. Some time ago I've found the following `let-alias' macro that does
> just this:

Ah, I suspected that syntax-case supported something like this.

> (use-syntax (ice-9 syncase))
>
> (define-syntax let-alias
>   (syntax-rules ()
>     ((_ ((id alias) ...) body ...)
>      (let-syntax ((helper (syntax-rules ()
>                             ((_ id ...) (begin body ...)))))
> 	(helper alias ...)))))
>
> ;; And here's the code for the aforementioned with-object-slots and let-slots:
>
> (use-modules (oop goops))
> (define slot-ref (make-procedure-with-setter slot-ref slot-set!))
>
> (define-syntax with-object-slots (syntax-rules ()
>                                   ((_ (object (alias1  slot1) ...) expr1 ...)
>                                    (let-alias ((alias1 (slot-ref
> object (quote slot1))) ...)
>                                      expr1 ...))
>                                   ((_ (object prop1 ...) expr1 ...)
>                                    (let-alias ((prop1 (slot-ref object
> (quote prop1))) ...)
>                                      expr1 ...))))
>
> (define-syntax let-slots (syntax-rules ()
>                            ((_ () expr1 ...)
>                             (begin expr1 ...))
>                            ((_ (binding1 binding2 ...) expr1 ...)
>                             (with-object-slots binding1
>                                                (let-slots (binding2 ...)
>                                                  expr1 ...)))))

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