[TUHS] [TUHS} Qed vs ed
M Douglas McIlroy
m.douglas.mcilroy at dartmouth.edu
Mon Feb 1 14:24:05 AEST 2021
> fairly early in PDP-11 development ed gained three features: & in the
> rhs of substitutions plus k and t commands. (I'm not sure about & ....
Oh, and backreferencing, which took regular expressions way up the
complexity hierarchy--into NP-complete territory were it not for the limit
of 9 backreferenced substrings. (Proof hint: reduce the knapsack problem to
an ed regex.)
Also g and s were generalized to allow escaped newlines.
I was indeed wrong about &. It was in v1.
Doug
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