StarLogo Project:
Tree
WHAT IS IT?
Drawing recursive trees is a standard project in programming
languages like Lisp and Logo. StarLogo makes possible new
types of recursive trees that are more "natural" and easier
to understand. Rather than using a single turtle to draw the
entire tree, the StarLogo approach "hatches" a set of new
turtles to draw each level of the tree.
HOW TO USE IT
Click the TREE button to draw a StarLogo tree.
The dist slider controls the length of branches in the tree.
The angle slider controls the angles between the branches.
The depth slider controls the depth of the tree.
THINGS TO NOTICE
Each level of the tree is drawn in parallel. That is, the
program draws the trunk, then the next two branches, then
the next four sub-branches, and so on. In the standard
Lisp/Logo approach for drawing recursive trees, the drawing
order is very different: the program draws all of the
leftmost branches of the tree and then works its way over
until it draws all of the rightmost branches. The StarLogo
approach seems much more natural and intuitive.
EXPLORATIONS
By adjusting the sliders, you can make some patterns that
look more like "creatures" than trees. Try it.
Modify the underlying program to add some randomness. What
changes are needed to make the tree look more like a "real"
tree?
STARLOGO FEATURES
In the treestep procedure, the "counter" for the recursion
is kept as a local turtle variable, not as a local procedure
variable.
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