Teachpacks for How to Design Programs

# Show Queen

### show-queen.ss

The teachpack `show-queen.ss` provides the operation `show-queen`. It implements a GUI for exploring the n-queens problem.

The function `show-queen` consumes a list of lists of booleans that describes a board. Each of the inner lists must have the same length as the outer list. The `true`s correspond to positions where queens are, and the `false`s correspond to empty squares. The function returns nothing.

In the GUI window that `show-queen` opens, the red and orange dots show where the queens are. The green dot shows where the mouse cursor is. Each queen that threatens the green spot is shown in red, and the queens that do not threaten the green spot are shown in orange.