How to test if symbol from string exists?

How to test if symbol from string exists?

[Jean Louis]

I would like to test if symbol exists and is true.

First I have string, like "people", then I can do this:

(symbol-value (intern "rcd-db-people-mode-map")) and it gives me
result.

But before asking for the value, I would like to test if symbol
exists. So I am trying this:

(bound-and-true-p (intern "rcd-db-people-mode-map"))

and I get error:

Wrong type argument: symbolp, (intern "rcd-db-people-mode-map")

as what I am trying to accomplish is to stop updating this function
with the one below that still does not work:

(defun rcd-db-table-mode-map (table)
  (cond ((string= "accounts" table) rcd-db-accounts-mode-map)
	((string= "acks" table) rcd-db-acks-mode-map)
	((string= "addressbookentries" table) rcd-db-addressbookentries-mode-map)
	((string= "areas" table) rcd-db-areas-mode-map)
	((string= "categories" table) rcd-db-categories-mode-map)
	((string= "countries" table) rcd-db-countries-mode-map)
	((string= "devt" table) rcd-db-devt-mode-map)
	((string= "edit" table) rcd-db-edit-mode-map)
	((string= "emails" table) rcd-db-emails-mode-map)
	((string= "groups" table) rcd-db-groups-mode-map)
	((string= "locationsets" table) rcd-db-locationsets-mode-map)
	((string= "mailinglistoptions" table) rcd-db-mailinglistoptions-mode-map)
	((string= "notes" table) rcd-db-notes-mode-map)
	((string= "pages" table) rcd-db-pages-mode-map)
	((string= "people" table) rcd-db-people-mode-map)
	((string= "skills" table) rcd-db-skills-mode-map)
	((string= "sms" table) rcd-db-sms-mode-map)
	((string= "statsdefinitions" table) rcd-db-statsdefinitions-mode-map)
	(t rcd-db-mode-map)))

so I would like replacing above function with the one here below,
which is now not working until I solve the problem how to verify for
the symbol existence, which symbol name I get from string.

(defun rcd-db-table-mode-map (table)
  (let ((symbol (intern (format "rcd-db-%s-mode-map" table))))
  (if (bound-and-true-p symbol)
      (symbol-value symbol)
    rcd-db-mode-map)))


Thank you,
Jean

Re: How to test if symbol from string exists?

[Gregory Heytings]

>
> I would like to test if symbol exists. So I am trying this:
>
> (bound-and-true-p (intern "rcd-db-people-mode-map"))
>
> and I get error:
>
> Wrong type argument: symbolp, (intern "rcd-db-people-mode-map")
>

That's because bound-and-true-p quotes its argument.  You can use another 
macro for that:

(defmacro bound-and-true-symbol-p (name)
   "Return the value of symbol with name NAME if it is bound, else nil."
   `(and (boundp (intern ,name)) (symbol-value (intern ,name))))

Re: How to test if symbol from string exists?

[Philip Kaludercic]

Jean Louis <bugs@gnu.support> writes:

> I would like to test if symbol exists and is true.
>
> First I have string, like "people", then I can do this:
>
> (symbol-value (intern "rcd-db-people-mode-map")) and it gives me
> result.

I think you want to use intern-soft, to return a symbol if it exists,
and nil if it doesn't. If you want to check if it is "used", boundp
should suffice, regardless of whether you use intern or intern-soft.

> But before asking for the value, I would like to test if symbol
> exists. So I am trying this:
>
> (bound-and-true-p (intern "rcd-db-people-mode-map"))

That is because bound-and-true-p is a macro.

> and I get error:
>
> Wrong type argument: symbolp, (intern "rcd-db-people-mode-map")
>
> as what I am trying to accomplish is to stop updating this function
> with the one below that still does not work:
>
> (defun rcd-db-table-mode-map (table)
>   (cond ((string= "accounts" table) rcd-db-accounts-mode-map)
> 	((string= "acks" table) rcd-db-acks-mode-map)
> 	((string= "addressbookentries" table) rcd-db-addressbookentries-mode-map)
> 	((string= "areas" table) rcd-db-areas-mode-map)
> 	((string= "categories" table) rcd-db-categories-mode-map)
> 	((string= "countries" table) rcd-db-countries-mode-map)
> 	((string= "devt" table) rcd-db-devt-mode-map)
> 	((string= "edit" table) rcd-db-edit-mode-map)
> 	((string= "emails" table) rcd-db-emails-mode-map)
> 	((string= "groups" table) rcd-db-groups-mode-map)
> 	((string= "locationsets" table) rcd-db-locationsets-mode-map)
> 	((string= "mailinglistoptions" table) rcd-db-mailinglistoptions-mode-map)
> 	((string= "notes" table) rcd-db-notes-mode-map)
> 	((string= "pages" table) rcd-db-pages-mode-map)
> 	((string= "people" table) rcd-db-people-mode-map)
> 	((string= "skills" table) rcd-db-skills-mode-map)
> 	((string= "sms" table) rcd-db-sms-mode-map)
> 	((string= "statsdefinitions" table) rcd-db-statsdefinitions-mode-map)
> 	(t rcd-db-mode-map)))
>
> so I would like replacing above function with the one here below,
> which is now not working until I solve the problem how to verify for
> the symbol existence, which symbol name I get from string.
>
> (defun rcd-db-table-mode-map (table)
>   (let ((symbol (intern (format "rcd-db-%s-mode-map" table))))
>   (if (bound-and-true-p symbol)
>       (symbol-value symbol)
>     rcd-db-mode-map)))
>
>
> Thank you,
> Jean
>
>

-- 
	Philip K.

Re: How to test if symbol from string exists?

[Jean Louis]

* Philip Kaludercic <philipk@posteo.net> [2021-04-16 12:23]:
> Jean Louis <bugs@gnu.support> writes:
> 
> > I would like to test if symbol exists and is true.
> >
> > First I have string, like "people", then I can do this:
> >
> > (symbol-value (intern "rcd-db-people-mode-map")) and it gives me
> > result.
> 
> I think you want to use intern-soft, to return a symbol if it exists,
> and nil if it doesn't. If you want to check if it is "used", boundp
> should suffice, regardless of whether you use intern or intern-soft.

Thanks, I made it this way here:

(defun rcd-db-table-mode-map (table)
  (let ((symbol (format "rcd-db-%s-mode-map" table)))
  (if (intern-soft symbol)
      (symbol-value (intern symbol))
    rcd-db-mode-map)))

as that replaces now the function below and I can just add new
function with new string to invoke either the default or specialy
defined mode map.

;; (defun rcd-db-table-mode-map (table)
;;   (cond ((string= "accounts" table) rcd-db-accounts-mode-map)
;; 	((string= "acks" table) rcd-db-acks-mode-map)
;; 	((string= "addressbookentries" table) rcd-db-addressbookentries-mode-map)
;; 	((string= "areas" table) rcd-db-areas-mode-map)
;; 	((string= "categories" table) rcd-db-categories-mode-map)
;; 	((string= "countries" table) rcd-db-countries-mode-map)
;; 	((string= "devt" table) rcd-db-devt-mode-map)
;; 	((string= "edit" table) rcd-db-edit-mode-map)
;; 	((string= "emails" table) rcd-db-emails-mode-map)
;; 	((string= "groups" table) rcd-db-groups-mode-map)
;; 	((string= "locationsets" table) rcd-db-locationsets-mode-map)
;; 	((string= "mailinglistoptions" table) rcd-db-mailinglistoptions-mode-map)
;; 	((string= "notes" table) rcd-db-notes-mode-map)
;; 	((string= "pages" table) rcd-db-pages-mode-map)
;; 	((string= "people" table) rcd-db-people-mode-map)
;; 	((string= "skills" table) rcd-db-skills-mode-map)
;; 	((string= "sms" table) rcd-db-sms-mode-map)
;; 	((string= "statsdefinitions" table) rcd-db-statsdefinitions-mode-map)
;; 	(t rcd-db-mode-map)))

-- 
Jean

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