/usr/share/doc/ruby-gsl/examples/sf/gegenbauer.rb is in ruby-gsl 2.1.0.3+dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | #!/usr/bin/env ruby
require("gsl")
n = 100
x = GSL::Vector.linspace(0, 5, n)
y1 = GSL::Sf::gegenpoly_1(0, x)
y2 = GSL::Sf::gegenpoly_2(0, x)
y3 = GSL::Sf::gegenpoly_3(0, x)
GSL::Vector.graph(x, y1, y2, y3, "-T X -C -g 3 -X x -L 'Gegenbauer functions'")
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