Thank you for the kind words! Zaki did allude to work on speed: Of note are several speed improvements.

• The shortcutting will be due to expanding what was already there, now referred to in the Ufunc code (following R.S. Bird's naming of it) as "left zeroes" (in commit https://github.com/PDLPorters/pdl/commit/58df094ff320183bc983227f0854982fc3c5e782).
• The speeding up of the full scan is slightly mysterious, and I'd be highly interested if you could do a git bisect to see which change caused that?

The "add loop" stuff is only relevant for those who write PP code, but it does make doing so much, much nicer.

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