[garethrees]

McIlroy's claim was not that his script is the shortest possible way to implement the task, but rather that the Unix philosophy of combining general-purpose tools operating on text streams is a better engineering approach than Knuth's special-purpose program, because the general-purpose tools can be reused in many ways.

McIlroy: "A first engineering question to ask is: how often is one likely to have to do this exact task’? Not at all often, I contend. It is plausible, though, that similar, but not identical, problems might arise. A wise engineering solution would produce—or better, exploit—reusable parts." [1]

[1] https://www.cs.tufts.edu/~nr/cs257/archive/don-knuth/pearls-...

[lqet]

My initial comment was easy to misunderstand, sorry: I was just wondering whether the additional A-Z check was doing something I was not aware of.

[garethrees]

It's slightly more efficient to squeeze non-alphabetic characters first and then convert to lowercase, rather than vice versa, because in the former case most of the non-alphabetic characters only get processed once, compared to twice in the latter case.