In this part, we present features to extend Dr.Geo’s capabilities, or to adapt it to a given pedagogical situation.
The first feature is the macro construction. It lets the user record a sequence of construction steps in a single command. Once recorded, it can be replayed and saved in a file to be opened later in another sketch.
the Dr.Geo Smalltalk script is another feature to extend Dr.Geo behaviour. A script appears as a sketch item like any other. As input, it can expect zero, one, or more references to geometric items from the sketch, and it returns a reference whose print representation is placed in the sketch. It is in fact a programmed method 4 placed in a sketch, and evaluated each time the whole sketch is updated (i.e. when the sketch need to be redrawn). A Dr.Geo Smalltalk script may be useful for its returned object or for its side effects, depending on the wishes of the user.
Going a step further, Dr.Geo offers Smalltalk sketches. In this case the whole interactive geometry sketch is described in Smalltalk source code. Its interest is the functional approach to describing a sketch5 compared to the linear, declarative method of constructing a sketch with the mouse.