Get symbol values for packages that might not exist. Use SYMLOOK to find variables in potentially nonexistent packages, and use SYMCALL to call functions in packages that may not exist. Tossed SYMBOUNDP into the mix as well; this function tests to see whe

gistfile1.lisp

(defun symbol-lookup (package-designator symbol &key (symbol-lookup-function #'symbol-value))
  (let ((return-value (list nil nil))
        value-of-symbol)
    (alexandria:when-let* ((package (find-package package-designator))
                           (found-symbol (find-symbol (symbol-name symbol)
                                                      package)))
      (setf value-of-symbol (ignore-errors (funcall symbol-lookup-function found-symbol)))
      (setf return-value
            (list value-of-symbol t)))
    (values-list return-value)))

(defun symbol-bound-p (package-designator symbol)
  (let ((package (find-package package-designator))
        found-symbol
        external-or-internal)
    (when package
     (multiple-value-setq (found-symbol external-or-internal)
       (find-symbol (symbol-name symbol)
                    package))
     external-or-internal)))

(defmacro symlook (package symbol)
  `(symbol-lookup (quote ,package) (quote ,symbol)))

(defmacro symcall (package symbol &rest parameters)
  (alexandria:with-gensyms (symbol-value symbol-present)
    `(multiple-value-bind (,symbol-value ,symbol-present)
         (symbol-lookup (quote ,package) (quote ,symbol) :symbol-lookup-function #'symbol-function)
       (if ,symbol-present
           (funcall ,symbol-value ,@parameters)
           (error (concatenate 'string
                               "Could not find function #'"
                               ,(symbol-name package)
                               "::"
                               ,(symbol-name symbol)))))))

(defmacro symboundp (package sym)
  `(symbol-bound-p (quote ,package)
                   (quote ,sym)))