> > Sam and Acme use a simple, pure form of regular expressions. If they
> > had the counting operations, this would be a trivial task, but to add
> > them would open the door to the enormous, ill-conceived complexity of
> > (no longer) regular expressions as the open source community thinks of
> > them.
>
> Is it really so? R. Cox (Regular Expression Matching Can Be Simple And
> Fast), I think, shows, that repetition can be first expanded and then
> used even by the nice (non-backtracking) algorithms, like this:
>
> e{3} --> eee
> e{3,5} --> eeee?e?
> e{3,} --> eee+
>
> where would the problem arise?
adding repetition would break many previously-
working regular expressions (any with '{'). a
command line switch to all programs using regular
expressions would be unacceptable. putting that
aside and getting to the heart of the question....
this is plan 9. we don't ask if new feature
x would not cause a problem, we ask if x
would make plan 9 a better system. i'm
quite sure one would be wrong in assuming
that plan 9's designers did not know about
repetition. i think it would be safer to assume
they were not keen on the idea.
- erik
