Re: Three questions about pcase for Stefan

[Stefan Monnier]

> i.e., floats do not count as "atom".  This is consistent, also explained
> correctly in the doc, but may nonetheless be confusing.  What led you to
> this decision?

Testing equality of floating point numbers is very rarely correct.

> 2.  Do you think we can already bury the old deprecated special behavior
> of the atoms nil and t as patterns?

Far from that.  IIUC, it's even still used in a GNU ELPA package.
We'll have to live with it for a reasonably long time.
And to tell you the truth, I don't think it's a great idea to make nil
and t match themselves.  We can plan on making them signal errors, OTOH
(for Emacs-26.1 or Emacs-27.1).

> 3.  Is it correct to say that not only the functions used in a pred
> pattern, but any ordinary Lisp code part of any pattern (guard, app,
> let, etc.) should be pure in the same sense?

Yes.


        Stefan