8 Extensions to the Tcl/Tk language in this program.

In order to implement the extra-focal image reduction algorithm in an efficient manner, several new commands have been added to the standard Tcl interpreter. In this chapter we will describe the new commands. The interpreter also comes with the BLT (Tk Graphics extension) library.

All the Tcl commands implemented here, are based upon the object model. Each of the Tcl commands creates a named object and associates a command with it. This mode of operation is similar to that used by Tk widgets. You should declare each of these objects at the global level. All of the following objects inherit functionality from our Tcl base class, then add some of their own functionality, and possibly replace the base class functionality. The base class recognizes the following commands:

1. [class] Returns a string naming the most senior class in the objects class hierarchy.
2. [delete] Destroys the object, and removes its associated command.
3. [status] Reports the status of the object.