Re: let*: Wrong type argument: stringp, nil

[Hongyi Zhao <hongyi.zhao@gmail.com>]

On Wed, Sep 29, 2021 at 9:43 AM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Tue, Sep 28, 2021 at 4:02 PM Yuri Khan <yuri.v.khan@gmail.com> wrote:
> >
> > On Tue, 28 Sept 2021 at 10:08, Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> >
> > > Now I'm trying another test code snippet based on the idea posted here [1]:
> > >
> > >     (while (not (file-exists-p ".python-version"))
> > >           (cd "..")
> > >     ))
> > >
> > > But when I test the above code in scratch buffer, it seems to be stuck
> > > in an endless loop and running there all the time. Any hints for this
> > > problem?
> >
> > You’re not handling the case here that you reached the root directory
> > without finding a .python-version file.
> >
> > You will really get better results if you use locate-dominating-file.
> > If you’re trying to learn, learn by reading that function. As a bonus,
> > it does not mess with the buffer’s default directory.
>
> I work out the following code snippets using locate-dominating-file,
> and it works as expected:
>
> (defun try/pyvenv-workon ()
>   (when (locate-dominating-file (buffer-file-name) ".python-version")

The following form should be used here:

(when (and (buffer-file-name) (locate-dominating-file
(buffer-file-name) ".python-version"))

>       ;https://emacs.stackexchange.com/questions/9474/let-statement-throws-error-on-assigning-a-form-to-a-variable
>       (let ((file (concat (locate-dominating-file (buffer-file-name)
> ".python-version") ".python-version")))
>            (pyvenv-workon (with-temp-buffer
>                            (insert-file-contents file)
>                              (nth 0 (split-string (buffer-string))))))))
>
>
> BTW, should I use `let' or `let*' here?
>
> HZ