Re: [Emacs-diffs] master 4612b2a 1/2: Implement and-let*

[Michael Heerdegen <michael_heerdegen@web.de>]

Richard Stallman <rms@gnu.org> writes:

>   > >     (internal--build-binding-value-form): Extend to account for
>   > >     solitary symbols and (EXPR) items in binding varlist.
>
>   > We're forced to accept those forms in `let` and `let*` for historical
>   > reasons,
>
> It is not just a matter of history.
> Those are very convenient in 'let'.
> It would be a bad idea not to have them.

> Whether they are useful in other new constructs, I don't know.
> What do these new constructs look like?

Just search for SRFI 2, e.g.

  https://www.gnu.org/software/guile/manual/html_node/SRFI_002d2.html

`if-let*' and `when-let*' in Emacs are analogue.

I don't know much about Lisp's history, but I think there was a
misunderstanding about what these special binding forms mean.  For
example, making a binding form consisting of a single symbol mean "bind
the symbol to nil" would not make sense in these new constructs -
instead, we test the symbol's value for nilness.


Michael.