Re: Question on pcase

[Andreas Schwab]

Oleh Krehel <address@hidden> writes:

> But the code that binds the variables, e.g. (setq thing x) will likely
> be hard to implement. For instance, look at this example with macroexpand:
>
> (setq test '(1 . 2))
> (pcase test
>   (`(,foo . ,baz)
>     (cons baz foo)))
> ;; =>
> ;; (2 . 1)
>
> (macroexpand '(pcase test
>                (`(,foo . ,baz)
>                 (cons baz foo))))
> ;; =>
> ;; (if (consp test)
> ;;     (let* ((x (car test))
> ;;            (x (cdr test)))
> ;;       (let ((baz x)
> ;;             (foo x))
> ;;         (cons baz foo)))
> ;;   nil)
>
> The macroexpanded code returns (2 . 2) when evaluated. This I don't
> understand.

Try binding print-gensym and print-circle to non-nil while the form is
printed.

Andreas.

-- 
Andreas Schwab, SUSE Labs, address@hidden
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