Topic awaiting preservation: Linear Algebra...help with Maple

Trying to code an algorithm in Maple from this paper.
http://www.cs.cornell.edu/cv/ResearchPDF/PolygonSmoothingPaper.pdf

Keeps crashing or giving invalid input errors. From page 3.

quote:

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1.2. Iteration: A First Try. There is no better way to develop an intuition
about repeated polygon averaging than to display graphically the progression from
one polygon to the next.
Algorithm 1
Input: Unit 2-norm n-vectors x(0) and y(0).
Display P0 = P(x(0), y(0)).
for k = 1, 2, . . .
% Compute Pk = P(x(k), y(k)) from Pk−1 = P(x(k−1), y(k−1))
x(k) = Mnx(k−1)
y(k) = Mny(k−1)
Display Pk.
end

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