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Re: WGLC on draft-freed-sieve-ihave-02.txt

2008-09-13 23:35:42

Stephan Bosch writes:
> Given the fact that most extensions introduce new language elements,
> the compiler must have some means of ignoring/discarding the regions
> of the script that need the obscure extensions.

Most extensions do not extend the grammar. They only add new commands,
tests, etc., which follow the basic Sieve grammar.

> Alternatively, doing the actual ihave test at runtime requires that
> the compiler can distinguish between erroneous language features and
> features that would have been introduced by the unknown extension (in
> order to produce compile time errors or runtime errors respectively).
> This would require knowledge about that obscure extension.

I think there's an unstated requirement there: in order to be used with
ihave, an extension must obey the grammar on page 36 of RFC 5228.

I can and will put this in as as requirement, but my understanding has always
been that extensions would not change the base grammar because doing so
requires that implementation change their core parsers - not good.