[TUHS] [TUHS} Qed vs ed

[TUHS] [TUHS} Qed vs ed

[M Douglas McIlroy]

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> 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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[TUHS] [TUHS} Qed vs ed

[M Douglas McIlroy]

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I used Ken's qed in pre-Unix days. I understand its big departure from the
original was regular expressions. Unix ed was the same, with
multi-file capability dropped. Evidently the lost function was not much
missed, for it it didn't come back when machines got bigger. I remember
that 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 &--that was
50 years ago.).

 With hindsight it's surprising that a "minimalist" design had m but not t,
for m can be built from t but not vice versa. A cheat sheet for multics qed
is at h
<http://www.bitsavers.org/pdf/honeywell/multics/swenson/6906.multics-condensed-guide.pdf>
ttp://
www.bitsavers.org/pdf//honeywell/multics/swenson/6906.multics-condensed-guide.pdf.
It had two commands I don't remember: sort(!) and transform, which I assume
is like y in sed.

Doug

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