Re: Indirect left recursion in iXML grammars

Steven Pemberton <steven.pemberton@cwi.nl> writes:
> This is what I mean by ixml can handle left-recursion:

I think technically what you’ve demonstrated is that iXML can express grammars with indirect left recursion and your implementation can successfully process grammars that contain it. I don’t think either of those two points was ever in dispute.

Our spec has five “hints for implementors” that explain how to transform the novel constructs of iXML into more standard ones.

Suppose we wanted to add a hint about how to eliminate indirect left recursion using the same sorts of mechanisms. Is that possible without changing the grammar such that it’s impossible to obtain the correct XML output? (How to remove indirect left recursion is well documented, but it works by rewriting the grammar in ways that appear to distort the structure beyond the ability to preserve the iXML structure.)
Is it known to be impossible?

I don’t think anyone is suggesting that we need to do this or even want to, but the underlying questions in grammar theory are interesting nevertheless.

                                        Be seeing you,
                                          norm

--
Norm Tovey-Walsh
Saxonica

Received on Tuesday, 10 February 2026 07:25:34 UTC