Re: Determine object passed as argument

Heime <[email protected]> writes:

> On Sunday, April 12th, 2026 at 3:27 AM, Heime <[email protected]> wrote:
>
>> 
>> >
>> > Or,
>> >
>> >   (defun lana-du-fpln (datenstruk &optional bname)
>> >     (if (cl-typep datenstruk 'symbol)
>> >       (symbol-name datenstruk)
>> >       ;; Else
>> >       "Not a symbol"))
>> >
>> >   (lana-du-fpln 'fpln)
>> >   => "fpln"
>> >   (lana-du-fpln '(a b c))
>> >   => "Not a symbol"
>> >   (lana-du-fpln "abc")
>> >   => "Not a symbol"
>> 
>> No need for boundp as outlines by Jean?
>
> Can I use (symbolp datenstruk)
>
> If the test fails and is not a symbol, then what is the
> argument?  Anonymous?
>

If the condition ‘(cl-typep datenstruk 'symbol)’ evaluates
to nil, then ‘datenstruk’ is not a symbol.

> Can I determine whether the input is a hash-table, plist, 
> alist or something else?
>

In that case, you do not have a simple conditional
expression:

   (if my-condition 
      then-expression
    else-expression)

Instead, you have a multi-branch conditional.  Because your
conditional is to branch based on the type of the parameter,
you can use ‘cl-typecase’:

  (defun report-a-type (obj)
    (cl-typecase obj
      (symbol "It’s a symbol")
      (hash-table "It’s a hash table")
      (plist "it’s a plist")
      ;; Need to define the predicate ‘alistp’:
      (list (if (alistp obj)
                "It’s an assoc. list"
              "It’s a list"))
      (t "Some other type")))

  (report-a-type 'k1)
  => "It’s a symbol"
  (report-a-type (make-hash-table))
  => "It’s a hash table"
  (report-a-type '(k1 v1 k2 v2 k3 v3))
  => "it’s a plist"
  (report-a-type '(key1 val1 key2))
  => "It’s a list"
  (report-a-type '((k1 v1) (k2 v2) (k3 v3)))
  => "It’s an assoc. list"
  (report-a-type '(() () ()))
  => "It’s a list"
  (report-a-type '((nil) (nil) (nil)))
  => "It’s an assoc. list"

Someone may have written a library/package that I am unaware
of that defines the equivalent of ‘alistp’ or an
association-list type.

See:

  (info "(cl) Type Predicates")
  (info "(elisp) Association List Type")

-- 
The lyf so short, the craft so long to lerne.
- Geoffrey Chaucer, The Parliament of Birds.