Copy/Paste the following code to your GroIMP project:
//**********************************************************
/*
You will learn with this example:
– how to insert simple imperative XL code directly into a rule,
– how to assign objects (nodes of the graph) during their generation
on the right-hand side of a rule by names and how to use them directly
in XL code,
– that by replacement, all attributes get lost when the objects are
replaced,
– that it is possible to transfer attributes from the left-hand side
of a rule to its right-hand side, if you take care of this
(e.g., the length of F is saved by the variable x)
*/

// the Koch curve again
protected void init()
// rule blocks must be enclosed in [] brackets
[
// a coloured triangle as the start word
// In braces { }, imperative XL code is specified: Here, the
// specification of the colour.
// The Objects are directly named when they are generated
// (names f1, f2).
Axiom ==> f1:F(10) { f1.setColor(0x0000ff); } RU(120)
f2:F(10) { f2.setColor(0xff0000); } RU(120) F(10);
]

public void derivation()
[
// replacement rule
F(x) ==> F(x/3) RU(-60) F(x/3) RU(120) F(x/3) RU(-60) F(x/3);
]

//**********************************************************