----------------
 Insertion sort
----------------

Sorts an array of values using insertion sort;
https://en.wikipedia.org/wiki/Insertion_sort

function insertion_sort(a)
	i=2
	while i < #a+1 do
		x=a[i]
		j=i-1
		while j>=1 and a[j] > x do
			a[j+1]=a[j]
			j=j-1
		end
		a[j+1]=x
		i=i+1
	end
end