Indeed, thanks to its API, it is possible to add scripts - small pieces of Smalltalk code - to interactive geometry sketches. Moreover one can also describe sketches entirely in Smalltalk source code. In previous post I already presented thus features, there are now fully explained in the Dr. Geo user guide (by the way volunteers to translate this guide in other languages are welcome and can contact me at

To ease the writing of code, Dr. Geo II now comes with a collection of developer tools:

  • Workspace, a text editor to write or to paste Smalltalk code and to compile and execute it. When executing this code, it is possible to execute in step-by-step mode through the debugger or to profile its execution time.
  • Debugger, to run step by step a Smalltalk code describing a sketch. The Debugger can be called explicitly with the self halt. statement.
  • Inspector, to examine and to modify the state of a specific object. Each object can be explicitly inspected by sending the message inspect, for example: segment inspect.
  • Class Browser, to examine and to modify the Dr. Geo II source code from Dr. Geo II itself.
  • Finder, to search and to find methods with a given behavior.

The screen shot below shows these tools in a Dr. Geo II session. Of course such session can be saved and restored later (including debugging phase):

Dr. Geo II programming session