On Mon, 4 Jan 2021, 2:19 am Barry Scott, <ba...@barrys-emacs.org> wrote:
>
> I quickly read 642 v3 and missed an explanation about why the syntax to
> match a string object is
> str{} and not str. Are you saying that I MUST use {} so that when case is
> parsed its clear that its a class
> with no constraints?
>
Yes. "str{}" would give a pure subclass check, "str()" would also be
allowed for classes that define "__match_args__".
> in the "Changes to class patterns" I read the BinaryOp example and
> I thought from the above that it would also use {} and not ().
>
> ---
>
> match expr:
>
> case BinaryOp(== '+', as left, as right):
>
> ---
>
> I was expecting to see:
>
> ---
>
> match expr:
>
> case BinaryOp{== '+', as left, as right}:
>
> ---
>
>
The example in the abstract doesn't show a class defined pattern that
relies on __match_args__, only an instance attributes pattern.
Cheers,
Nick.
>
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