Question

(defun find-attr (node attr)
    (let ((children (pt-children node)))
      (if (null children)
          nil
          (let ((subchildren (mapcar ##############

(get-value-if-attrib-present (node attrib) ...)

pt is a class. (pt-children node) yields children of node which are also pt objects. attr is a string. suppossing I write get-value-if-attrib-present to return the value of a pt object if it has the matching attr, how do i go about getting the list of all the values of subchildren of node with matching attr here (at ####….)?

Answer 1

For Common Lisp use one of these functions:

• REMOVE-IF
• REMOVE-IF-NOT
• REMOVE

They go over a list and remove items. Keep those which you want.

Other wise LOOP will do it:

(LOOP for item in some-list
      when (predicate-p item)
      collect it)

IT is a LOOP feature -> it refers to the value returned by the predicate in the WHEN clause.