Re: [CZT-Devel] cycles in section parents: parsing or typing error?

[Leo F. <leo...@ne...>]

Hi guys,

Many thanks for this. Our implementation is already in line with this, so will commit soon.

One technicality though: because LatexMarkupFunction is calculated earlier (e.g., as a lexer),
and teh information tables (e.g., optable, joker, thm, proofs, definition, etc) occur later on unicode
stream, and we want a solution that is markup independent, the treatment in the parser is to some
extent repeated for these two parts of the process - I don't think there is any performance penalty
for this (e.g., the process is already quite like that anyway - LMF first; tables later).

Best,
Leo


On 17 Jan 2012, at 21:38, Tim Miller wrote:

> It definitely belongs in the typechecker. There is a note in the 
> "inheriting section" section of the Z standard that says:
> 
> "NOTE 1 Ancestors need not be immediate parents, and a section cannot be 
> amongst its own ancestors (no cycles in the parent relation)."
> 
> It is not part of the type rule though, so I must have missed it when I 
> implemented the type rules.
> 
> Cheers,
> Tim
> 
> On 18/01/12 07:06, Mark Utting wrote:
>> Leo
>> 
>> Doing it in the typechecker sounds best to me.
>> 
>> 1. You might be able to give better error messages there.
>> 2. It will/should work on unicode input, not just latex input.
>> 
>> Cheers
>> Mark
>> 
>> On 18 January 2012 02:07, Leo Freitas <leo...@ne...
>> <mailto:leo...@ne...>> wrote:
>> 
>>    Hi,
>> 
>>    We are trying to solve the problem (e.g., stack overflow) involving
>>    cyclic parents of sections.
>>    The error occurs when calculating the latex markup function of
>>    parents during parsing.
>> 
>>    Our change/solution avoids the error, and enables sections with
>>    cyclic parents to be parsed.
>>    Next, the typechecker ensures that the cycle is an error (e.g., note
>>    1, p. 5, 13.2.2.1).
>> 
>>    So the question is, should the error be flagged by the parser or the
>>    typechecker?
>>    Looking at the standard, this we couldn't find where it would be. At
>>    the moment,
>>    we have it at the typechecker.
>> 
>>    Comments?
>> 
>>    Leo & Andrius
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