bug#31953: [VanL] Re: bug#31953: feature request - `highlight-rx` interactively

[Juri Linkov]

>> - ‘or’ has a synonym ‘|’, but ‘and’ has no synonym ‘&’
>
> `and' is not the counterpart of `or', it's a synonym for `seq' or `:'.
> We should probably deprecate `and', since this is a bit confusing.

I consider ‘rx’ as an analogue of Definite Clause Grammar.

I'm so accustomed to Prolog paradigms used for defining grammars in DCG
that I can't use `rx' without its analogous constructs, e.g. such DCG:

  rx --> a, b; c.

where ‘,’ denotes conjunction, and ‘;’ denotes disjunction,
would naturally translate in ‘rx’ to corresponding and/or:

  (rx (| (& a b) c))

For example, this package parses a regexp and returns a DCG structure:
https://github.com/SWI-Prolog/packages-regex/blob/master/regex.dcg.pl