Why does Hash.size return Int32 and not UInt32?

Crystal Contrib
21

I don’t reason about runtime part for now , but about compile-time part:
It is easy to modify example so it is still needed to iterate array manualy:

i = arr.size-1
while i >= 0
  yield(arr[i]) #block can add elements to array 
  i-=some_fun(arr[i]) # we skip some elements depending on  the value of processed element.
end

if I understand correctly it would have to be rewritten to something like

return if arr.size == 0
i = UInt32.new(arr.size)-1
loop do
  yield(arr[i])
  v = some_fun(arr[i]) 
  break if v > i
  i -= v
end