Thanks for the suggestion! natural-sort looks like what I want - I've just taken a quick look and the algorithm is almost the same if I'm not mistaken.
also thanks MarLinn - it's just that as I wrote I realized I've been implemented "tr" over and over again so there might be a common name for it. I do recognize there's a (***) out there
and hoogling (a, [a]) -> [a] doesn't yield any function of interest., didn't bother to go any further to see the rest of it is just a curried (:).
I'd still prefer "tr" though as for me if you think it as a rewrite rule, it's more readable than having a chain of function composition.
Cheers!