Re: Determine object passed as argument

On Sunday, April 12th, 2026 at 12:57 AM, Jean Louis <[email protected]> wrote:

> On 2026-04-11 15:14, Heime wrote:

> > Can a function determine the object being passed as argument and
> > print its name.  For instance that I passed if I pass fpln when
> > calling (lana-du-fpln 'fpln).
> >
> > (defun lana-du-fpln (datenstruk &optional bname)
> 
> In Emacs Lisp, you cannot directly get the variable name that was passed
> to a function, because arguments are evaluated before being passed. By
> the time datenstruk receives the value, the original variable name is
> lost.
> 
> (defun lana-du-fpln (datenstruk-symbol &optional bname)
>    "Print the name of the symbol passed, then access its value."
>    (message "Processing variable: %s" datenstruk-symbol)
>    (let ((datenstruk (symbol-value datenstruk-symbol)))
>      ;; Now work with datenstruk's value
>      (message "Value: %S" datenstruk)))
> 
> Call it with quoted symbol: (lana-du-fpln 'fpln)

The above gives "Warning: lana-fpln is unbound (void variable)"
 
> (defun lana-du-fpln (datenstruk-symbol &optional bname)
>    "Print the name of the symbol passed, then access its value if bound."
>    (message "Processing variable: %s" datenstruk-symbol)
>    (if (boundp datenstruk-symbol)
>        (let ((datenstruk (symbol-value datenstruk-symbol)))
>          (message "Value: %S" datenstruk)
>          ;; Your logic here
>          )
>      (message "Warning: %s is unbound (void variable)"
> datenstruk-symbol)))
> 
> "Warning: fpln is unbound (void variable)"

The above gives "Processing variable: fpln" followed by its value.

Why does the condition (if (boundp datenstruk-symbol) make things work out?

> --
> Jean Louis
> 
>