*NOT* the same. Sorry.... I hope the example explains better than my prose. -rob On Fri, Sep 17, 2021 at 7:32 PM Rob Pike wrote: > You'd have to ask ken why he chose the characters he did, but I can answer > the second question. The beginning and end of line are the same. If you > make ^ mean both beginning and end of line, what does this ed command do: > > s/^/x/ > > Which end gets the x? > > -rob > > > On Fri, Sep 17, 2021 at 7:00 PM markus schnalke wrote: > >> Hoi, >> >> I'm interested in the early design decisions for meta characters >> in REs, mainly regarding Ken's RE implementation in ed. >> >> Two questions: >> >> 1) Circumflex >> >> As far as I see, the circumflex (^) is the only meta character that >> has two different special meanings in REs: First being the >> beginning of line anchor and second inverting a character class. >> Why was it chosen for the second one? Why not the exclamation mark >> in that case? (Sure, C didn't exist by then, but the bang probably >> was used to negate in other languages of the time, I think.) >> >> 2) Symbol for the end of line anchor >> >> What is the reason that the beginning of line and end of line >> anchors are different symbols? Is there a reason why not only one >> symbol, say the circumflex, was chosen to represent both? I >> currently see no disadvantages of such a design. (Circumflexes >> aren't likely to end lines of text, neither.) >> >> I would appreciate if you could help me understand these design >> decisions better. Maybe there existed RE notations that were simply >> copied ... >> >> >> meillo >> >