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Subject: |
29.0.50; rx doc: Semantics of RX... |
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Date: |
Sun, 23 Oct 2022 04:32:17 +0200 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) |
Hello,
please document the semantics of multiple RXs for the RX repetition
operators (and maybe grouping operators, too).
The resulting regexps are concatenating like with an implicit `seq'.
This is not trivial, though: in stringish regexps the repetition
operators are only unary, and different interpretations would make sense
for `rx' (implicit `seq', implicit `or').
The docstring of `rx' doesn't tell anything about this. The manual has
sentences like
| ‘(zero-or-more RX...)’
| ‘(0+ RX...)’
| Match the RXs zero or more times. Greedy by default.
| Corresponding string regexp: ‘A*’ (greedy), ‘A*?’ (non-greedy)
but that suffers from the same problem that the semantics of A are not
clear: A == (seq RX...) ?
Oh, and maybe let's also make more clear that `rx' always cares about
implicit grouping when necessary. For example, in
(info "(elisp) Rx Constructs") it's not trivial that e.g. in
‘(seq RX...)’
‘(sequence RX...)’
‘(: RX...)’
‘(and RX...)’
Match the RXs in sequence. Without arguments, the expression
matches the empty string.
Corresponding string regexp: ‘AB...’ (subexpressions in sequence).
`rx' silently adds shy grouping to the result, and the corresponding string
regexp in this case is more precisely \(?:AB...\). I think it is enough
to mention this implicit grouping feature once, but it is important to
spell it out.
TIA,
Michael.
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--- Begin Message ---
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Subject: |
Re: 29.0.50; rx doc: Semantics of RX... |
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Date: |
Tue, 25 Oct 2022 04:49:20 +0200 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) |
Mattias Engdegård <mattias.engdegard@gmail.com> writes:
> > A sentence like "rx forms are defined by their semantics" would help
> > to make that clear I think.
>
> Well, I added a phrase to that effect as well.
Thanks - I hope it was not too much.
> Thank you for your comments and suggestions!
And thank you for the implementation of these!
Regards,
Michael.
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