Proposal: plug the space leak in transpose

[Henning Thielemann]

On Sun, 23 Aug 2020, David Feuer wrote:

> Data.List.transpose, unfortunately, can potentially leak space. The 
> problem is that it walks a list of lists twice: once to get the heads 
> and once to get the tails. Depending on the way the result is consumed, 
> it's possible that heads or tails that are never used will be retained 
> by the garbage collector. I have a fix[*] that probably makes the 
> function slower in typical cases, but that plugs the leak. What do y'all 
> say?

Your way sounds more correct than using 'head' and 'tail'. I have no 
numbers, though.