> But as you say, case folding is expensive. And with this approach you > are going to case-fold every string that is matched against an rx > that has some part of it that is case-insensitive.
That is correct in general. But regex compiler can be smarter than that. For example, rx should optimize /a+/i to /[aA]+/ to avoid case-folding. If it is too difficult for rx to do case-folding, I think it is better to use some normalizer to do full-case folding. > The case-folding should be done in the rx itself, at compile time if possible. > Then it is only done once, which will save a lot of time if the rx happens > to be used in a loop or something. The regular expression itself is case-folded at compile time. But I am talking about input string here, not re. Hong
