Re: [slightly OT]Universal Turing machine in XSLT

>  It seems to me that one of the implicit assumptions used by a UTM
> is that it is able to write any specified symbol.

any specified symbol from some specified finite alphabet. It would  be
enough to just have 0 and 1 as any finite alphabet can be encoded in
binary, it just needs a longer tape.

> If I read the XML
> spec correctly though, certain symbols are not legal (for example
> 0x0000 is not a valid Unicode codepoint). 

so, the set of symbols is the set of XML characters, the fact that there
are rather less of them than the unicode code of the highest doesn't
really matter.

David

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