On Tue, Jul 20, 2021 at 09:21:32PM +0800, Hongyi Zhao wrote:
> On Tue, Jul 20, 2021 at 8:49 PM <tomas@tuxteam.de> wrote:
> >
> > On Tue, Jul 20, 2021 at 07:12:14PM +0800, Hongyi Zhao wrote:
> > > I adapted the examples given on
> > > <https://www.gnu.org/software/emacs/manual/html_node/elisp/Association-Lists.html>
> > > to the following:
> > >
> > > ;;;
> > > (setq colors '(("rose merry" . red) (lily (belladonna . yellow))))
> > >
> > > (let-alist colors
> > >   (if (eq ."rose merry" 'red)
> > >       .lily.belladonna))
> > > ;;;
> > >
> > > When I try to evaluate the above code snippet, the following error is triggered:
> >
> > It's not the space. It's the dot ".". This is wrong Lisp syntax:
> >
> >   (eq ."rose merry" 'red)
> >
> > Also the dots in .lily.belladonna look strange. This will be the next
> > syntax error.
> >
> > BTW., if you take the dot out, like so
> >
> >   (eq "rose merry" 'red)
> 
> The dot syntax is described on
> <https://www.gnu.org/software/emacs/manual/html_node/elisp/Association-Lists.html>,
> as follows:
> 
> Macro: let-alist alist body
>
> Creates a binding for each symbol used as keys the association list
> alist
[...]

Oh -- thanks. Didn't know about `let-alist'. But if I read it correctly,
the macro wants to have symbols as keys, not other types (like strings).
Note the snippet of the doc quote above.

This works for me:

  (setq colors '((rose . "red") (lily . "white") (sunflower . "yellow")))

  (let-alist colors
    (format "a lily is %S\n" .lily))

  => a lily is "white"

It seems `let-alist' gets horribly confused if it tries to build a
variable binding from a string.

Cheers
 - t