Re: [O] About the use of PROPERTY "meta lines"...

[Eric Schulte]

Torsten Wagner <address@hidden> writes:

> Hmm...
> but this point is really interesting at least worse to write down in the 
> manual.
>  From my understanding a
> #+PROPERTY: var bar=2
> sets bar globally to 2
> somewhere and many lines and headers later
> #+PROPERTY: var bar=5
> would change this value to 5 for either the rest of the file or until a 
> new assignment is given...
> in that way a property line would be an tree-independent global variable
>

Two points here.
1) currently #+property: lines are global and affect the entire file
   regardless of where they are located in the file, there is no notion
   of different values before or after a particular #+property: line.
   So in the case above I would expect the var property to have the
   value bar=5 as the later line will most likely overwrite the former
   line.

2) there is nothing special about the "var" property which could make it
   behave differently than other properties.

>
> in contrast, a property-block is only valid of the given tree (and
> subtrees?).
>

true

>
> This brings up the question if there is a need for
>
> #+PROPERTY: const bar=2
>
> which would behave exactly the same like var but issue an error message 
> if someone tries to set it again somewhere in the file.
>

No, currently *all* properties are set in the same way regardless of
their name, and I think this is a simplification worth keeping.

Best,

>
> Torsten
>
>
>
> On 01/06/2012 04:28 PM, Eric Schulte wrote:
>> "Sebastien Vauban"<address@hidden>  writes:
>>
>>> Hi Eric and all,
>>>
>>> Eric Schulte wrote:
>>>> "Sebastien Vauban"<address@hidden>  writes:
>>>>
>>>>> #+TITLE:     Properties
>>>>> #+AUTHOR:    Seb Vauban
>>>>> #+PROPERTY: var  foo=1
>>>>> #+PROPERTY: var+ bar=2
>>>>>
>>>>> * Abstract
>>>>>
>>>>> IIUC, properties are set in this way:
>>>>>
>>>>> - on a file basis, before any heading, through the =PROPERTY= keyword,
>>>>> - on a subtree basis, through the =PROPERTIES= block.
>>>>>
>>>>> My comprehension is that the =PROPERTY= keyword may not be used inside 
>>>>> "trees",
>>>>> and should be ignored if that would happen.
>>>>
>>>> While it is not normal usage, I think that it is legal for #+PROPERTY:
>>>> lines (or #+Option: lines etc...) to appear inside of subtrees.
>>>
>>> I realize this is not especially a Babel question, but more a Org core
>>> question...
>>>
>>> Thanks for your answer -- which generates a new one, though: what is then 
>>> the
>>> expected *semantics* of such a construct?
>>>
>>> There are at least 3 different views on such a construct: putting a PROPERTY
>>> line inside a subtree...
>>>
>>> - ... resets some values from that point up to the end of the subtree
>>> - ... resets some values from that point up to the end of the buffer
>>> - ... defines some values which can have already been by the subtree
>>>
>>
>> I agree this is murky and whatever behavior we want should be clearly
>> thought out and documented in the manual.  I would argue that you missed
>> another possible semantics, the simple semantics which are currently
>> implemented in which a property line *anywhere* in a buffer sets a
>> global property.
>>
>> Cheers,
>>
>>>
>>> Best regards,
>>>    Seb
>>>
>>>>> The following example shows that either:
>>>>>
>>>>> - I'm wrong to think so,
>>>>> - there is a bug.
>>>>>
>>>>> What is the right assumption here?
>>>>>
>>>>> * Subtree
>>>>>
>>>>> Being located in a subtree, the following lines are ill-placed IMHO:
>>>>>
>>>>> #+PROPERTY: var  foo="Hello
>>>>> #+PROPERTY: var+ world"
>>>>>
>>>>> Though, they're well taken into account:
>>>>>
>>>>> #+begin_src emacs-lisp
>>>>>    foo
>>>>> #+end_src
>>>>>
>>>>> #+results:
>>>>> : Hello world
>>>>>
>>>>> These lines have even wiped the definition of =bar= (because of the use 
>>>>> of =var=
>>>>> without any =+=):
>>>>>
>>>>> #+begin_src emacs-lisp
>>>>>    (+ foo bar)
>>>>> #+end_src
>>>>>
>>>>> returns the error "Symbol's value as variable is void: bar."
>>
>

-- 
Eric Schulte
http://cs.unm.edu/~eschulte/