recurse.jl

# Fun with sequential differences
# @author jack@tinybike.net

# Recursion (hideous...or maybe I'm just bad at it)
function seqdiff!(x; top=NaN, differences=[])
    if isempty(x)
        return [0, differences], sum(differences)
    end
    if isnan(top)
        top = pop!(x)
    else
        prev = top
        top = pop!(x)
        differences = [prev - top, differences]
    end
    seqdiff!(x; top=top, differences=differences)
end

recursive_answer = seqdiff!([1, 2, 4, 6, 10, 15])

# Iteration
x = [1, 2, 4, 6, 10, 15]
differences = x[1:end] - [x[1], x[1:end-1]]
iterative_answer = (differences, sum(differences))

# Verify both answers are the same
@assert recursive_answer == iterative_answer

println("Recursion: ", recursive_answer)
println("Iteration: ", iterative_answer)