Re: Return value not as expected in Emacs Lisp function

[Thorsten Jolitz <tjolitz@gmail.com>]

"Pascal J. Bourguignon" <pjb@informatimago.com> writes:

> Thorsten Jolitz <tjolitz@gmail.com> writes:
>
>> and I ask myself what happened between the second-last and the last line of
>> the function? I cannot reproduce this with a MWE, and the real function is too
>> convoluted to present it here, so I keep the problem description on an
>> abstract level. 
>
> On an abstract leve, I can't debug a function if I don't have it's
> code.  That's the reason d'être of the MWE, and by default the real code.

I found the error, a misplaced paren. I could not reproduce the error in
a MWE - probably I did not copy the part with the misplaced paren to the
MWE.

>> I'm actually only interested in the result string as a return value, the
>> message statement is just for logging. But why is the string produced by
>> 'mapconcat' missing in the return value?
>
> The real question is why you use mapconcat to produce a string
> representation of a sexp?  Just use prin1-to-string!
>
> (let ((list '((click NIL 1) (press NIL 1) (click NIL 4) (click NIL 1))))
>   (prin1-to-string `(prog ,@list )))
> --> "(prog (click NIL 1) (press NIL 1) (click NIL 4) (click NIL 1))" 
>
> Notice:
>
> - emacs lisp is a lisp-2, not a lst-1.
>
> - NIL is true:
>   
>   (not (not 'NIL))       --> t
>   (not 'NIL)             --> nil
>   (if 'NIL 'true 'false) --> true


I should have said that this 

,-----------------------------------------------------------------
| "(prog (click NIL 1) (press NIL 1) (click NIL 4) (click NIL 1))"
`-----------------------------------------------------------------

is actually PicoLisp, a lisp-1 with NIL and T syntax (uppercase!). I
thought the 'prog in the beginning (PicoLisp's 'progn)  would make it
clear its not Elisp. At least C-h f doesn' show me a 'prog function in
Elisp. 

But thanks for your answer, I did not know `prin1-to-string', and finally
looked up the difference between lisp-1 and lisp-2. 

-- 
cheers,
Thorsten