An important skill in programming is being able to visualize the operation of procedures, both for constructing programs and debugging them. Tinker is a programming environment for Lisp that enables the programmer to "see what the program is doing" while the program is being constructed, by displaying the result of each step in the program on representative examples. To help the reader visualize the operation of Tinker itself, an example is presented of how he or she might use Tinker to construct an alpha-beta tree search program.
