ruby array length vs. capacity

arraycap.md

Based on reading https://github.com/ruby/ruby/blob/5a121a4f0b8fb9d416566f75047a190166d98609/array.c#L245-L258

Assuming code like:

array = []
loop { array.push(1) }

length	capacity
0	3
1	3
2	3
3	3
4	20 (4 + 16 (ARY_DEFAULT_SIZE))
...	...
20	20
21	37 (21 + 16 (ARY_DEFAULT_SIZE))
...	...
37	37
38	56 (38 + (37 / 2))
...	...
56	56
57	85 (57 + (56 / 2))
...	...
85	85
86	128 (86 + (85 / 2))