Rotation Matrix

gistfile1.rb

def cos *args
  Math.cos(*args)
end

def sin *args
  Math.sin(*args)
end

def funky_func(theta)
  proc do |x, y|
    [cos(theta) * x + -1 * sin(theta) * y, sin(theta) * x + cos(theta) * y]
  end
end

describe "math and stuff" do
  let(:theta) { rand * Math::PI / 2 }

  it "rotates into the first quadrant" do
    x, y = funky_func(theta).(1, 0)
    expect(x).to be_within(0.01).of(cos(theta))
    expect(y).to be_within(0.01).of(sin(theta))
  end

  it "rotates into the second quadrant" do
    x, y = funky_func(theta).(0, 1)
    expect(x).to be_within(0.01).of(-1 * sin(theta))
    expect(y).to be_within(0.01).of(cos(theta))
  end

  it "does other stuff" do
    x, y = funky_func(Math::PI/2).(0.5, 0.5)
    expect(x).to be_within(0.01).of(-0.5)
    expect(y).to be_within(0.01).of(0.5)
  end
end