Fractal

_Fractal_
_fractal_

This collection provides three file:

 _fractal.ss_: exports everything
 _model.ss_: just the underlying computations
 _window.ss_: the GUI code

This is a fun example of a simple fractal, similar to the Koch curve.

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DATA DEFINITIONS -----------------------------------------------------

A direction is one of:

  - 'N
  - 'E
  - 'S
  - 'W

A point is:

  - (cons nat nat)

A path is a non-empty list of points.


PROCEDURES -----------------------------------------------------------

> (fractal-window [w 300] [h 300]) :: [nat * nat] -> frame<%>

Displays a window with a fractal image. Click the window to advance to
the next iteration.

> (fractal-iteration n origin len) :: nat * point * nat -> path

Computes the path for iteration `n', starting at point `point' and with segment
length `len'.

> (directions-for n dir) :: nat * direction -> (listof direction)

Computes the segment directions for iteration `n', starting in direction `dir'.

> (path-for dirs origin len) :: (listof direction) * point * nat -> path

Computes the path for the directions `dirs' computed by _directions-for_, starting
at point `point' and with segment length `len'.