Empty matches on replace/all

[snan]

(irregex-replace/all
 (irregex '(: bos (* whitespace)))
 "any gosh darn string" "")

⇒ "aany gosh darn string"

With a + instead of a kleenstar it works.

[ashinn]

0.9.7 fixed some corner cases involving empty matches, causing this regression. It's surprisingly tricky to get these all right - I'm half tempted to just throw errors on empty matches :(

[snan]

Please do not throw errors on empty matches!

[ashinn]

I'm just grumbling and kicking myself for fixing the symptoms of the empty matches previously instead of the root cause.

[snan]

What I did for loop detection was to stop when we were string=? to the previous iter. That has turned out to be super expensive though.

[ashinn]

Just use irregex-fold for iteration, it does the work for you.

[snan]

I do use irregex-fold in another place in the code. The case where I used string=? for loop detection was for recursive re-matching from the start of the string. I.e. (strse "aaaaaaaah!" "aa" "a" #t) ⇒ "ah!" This isn't something irregex-fold is set up to do since it uses consecutive matching on the original string. Also, irregex-fold/fast isn't exported as far as I could tell so the way to use it is to use replace/all, which is what my "aaaaaah" thing does: calls replace/all again and again until it's satisfied.