The type of each piece of runtime data can be determined. The application program tests the type of the data before performing operations on it.

(defun copy-tree (x)
  (if (atom x) x
      (cons (copy-tree (car x))
            (copy-tree (cdr x))) ))

Advantages:

• Flexibility: The same code can work with many kinds of data.

• Speed: Need to test types repeatedly at runtime. Hardware support can help this problem.

• Verifiability: Harder to verify that a program will work for all combinations of data types.

Contents    Page-10    Prev    Next    Page+10    Index