lisp - Creating a keyword symbol -

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i'm trying create macro takes keyword parameters and, if parameter defined, add entries list. splitting following code should illustrate need.

(defun add-if-not-null (var lst)   (if (not (null var))       (append (cons (***) (cons ver '())) lst)))

the 3 asterisks show part i'm trying figure out. takes symbol name , turns keyword representation. e.g. width converts :width

(let ((width 100))     (add-if-not-null (width '())))

should return

(:width 100)

i'm using cl-who create svg representation , want set attributes width , height if specified parameters macro wraps document.

the name of package keyword. symbols created (if necessary) , put package using intern.

cl-user 11 > (intern (symbol-name 'width) "keyword") :width

a macro:

cl-user 29 > (defmacro add-if-not-null (var list)                (check-type var symbol)                `(when var                   (push (list ,(intern (symbol-name var) "keyword") var)                         ,list))) add-if-not-null  cl-user 30 > (macroexpand-1 '(add-if-not-null width some-list)) (when var (push (list :width var) some-list)) t

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