#= Preamble:
Import required modules, set up plotting, define various constants to be used later
==============================================================================#
using Plots
gr()

const r = 1
const n = 5
const δ = 2*r/1000    #1/1000th of the diameter used as fixed length


#= Generates a random point within a disk of radius r
==============================================================================#
function PointRandomDiskCartesian(r=1)
    while true
        Potential_Points = [rand()*(r*2)-r rand()*(r*2)-r]

        if norm(Potential_Points) <=r
            return Potential_Points
        end
    end
end


#= Generates matrix of n points within a disk radius r
==============================================================================#
function PointsRand(n, r=1)
    PointMatrix = zeros(n, 2)

    for i in 1:n
        PointMatrix[i, :] = PointRandomDiskCartesian(r)
    end
    return PointMatrix
end

#= Randomly increases/decreases one dimension of chosen random point by value δ
==============================================================================#
function RandomPerturbation(Points, r, δ)
    while true
        rand_point_index = rand(1:size(Points)[1])
        rand_x_or_y      = rand(1:size(Points)[2])
        rand_add_or_subt = rand([+1 -1])

        Potential_Points = Points[rand_point_index, :]
        Potential_Points[rand_x_or_y] += rand_add_or_subt*δ

        if norm(Potential_Points) <=r
            Points[rand_point_index, :] = Potential_Points
            return Points
        end
    end
end

OriginalPoints  = PointsRand(5) #Calls PointsRand getting 5 random Cartesian coordinates
println(OriginalPoints)         #Prints them now, so it can be checked later

PerturbedPoints = RandomPerturbation(OriginalPoints, r, δ) #Calls the perturbation function which takes in OritinalPoints and returns a perturbed version
println(PerturbedPoints) #Prints the perturbed points

println(OriginalPoints) #Prints the original points again

println(OriginalPoints.-PerturbedPoints) #Now perturbed and original points are equal... why?