bug#28254: 26.0.50; SRFI-2 and-let*

[Mark Oteiza <mvoteiza@udel.edu>]

On 12/09/17 at 02:39pm, Michael Heerdegen wrote:
> Mark Oteiza <mvoteiza@udel.edu> writes:
> 
> > Any comments?
> 
> Some notes on the documentation of `if-let*' after your patch:
> 
> |   "Bind variables according to VARLIST and eval THEN or ELSE.
> | Each binding is evaluated in turn with `let*',
> 
> Maybe comparing with `let*' is confusing after the change, because not
> all bindings must look like (SYMBOL EXPRESSION) any more.  I think when
> we just remove the two words "with `let*'", the documentation is still
> fine.

I agree, thanks.

> | and evaluation stops if a binding value is nil.  If all are non-nil,
> | the value of THEN is returned, or the last form in ELSE is returned.
> 
> Not really related to your change, but: Maybe we should additionally say
> that THEN can refer to the bindings made in the VARLIST, but ELSE to
> none, not even to those that resulted in non-nil values before
> "failing".

That's not true though--you can refer to the bindings in either branch:

    (if-let* ((x 2) (y nil)) x (list x y))

 => (let* ((x (and t 2)) (y (and x nil))) (if y x (list x y)))

> | Each element of VARLIST is a symbol (which is bound to nil) [...]
> 
> Did we agree that we drop this useless case?

Ah yes, this is no longer the case in this patch.  Good catch, thank
you.