Re: Calling a function with undefined symbol

[Jean Abou Samra]

Le 31/10/2022 à 09:15, Heime a écrit :
> Have written a function named "mbcomplt" that takes a symbol.
>
> (defun mbcomplt (sgnl)
>    "DOC."
>
> (if (eq sgnl 'go)
>      (message "go")
>    (message "nogo")))
>
> I can call this function with
>
> (mbcomplt 'go)
>
> This even though the symbol "'go" does not exist.  What is happening here?
>
> My understanding about symbols is that I can make a symbol using
>
> (defvar seqr 3)  ; set symbol seqr with value 3
> (setq seqr 5)    ; set symbol seqr with value 5
>
> (symbol-value 'seqr) ; get value of symbol (returns 5)
> (symbol-name 'seqr)  ; get name of symbol (returns "seqr")




It may be helpful to view symbols as some kind of modified
strings. The symbol 'go is an amorphous object, just a name
for something. You can use it as a name, or as a discrete
key, or whatever. You can also "define" it, or rather
define a variable with its name, and then you are able
to use symbol-value on it, but the symbol object itself is
a *potential* name and does not need to have a variable with
its name defined in order to be used.

Jean