Dan Davison <dandavis...@gmail.com> writes: > "Eric Schulte" <schulte.e...@gmail.com> writes: > >> [...] >>> >>> I agree, the things I was talking about don't end up being simpler in >>> terms of usage for this case. My thinking was that variable unsetting >>> might be something that would be required fairly rarely, and so it might >>> be worth appropriate to support it as part of a more general/powerful >>> mechanism tied into Org properties, or even that hook. >>> >> >> It does sound like if there were a way to disable inheritance for >> certain properties for certain sub-trees of a document, then that would >> be ideal -- although I can't imagine how such functionality would be >> implemented. Can we think of an Org-wide syntax for disinheriting >> specific properties? > > I'm not sure whether or how this fits it, but it's worth noting that Org > currently documents the following > > ,---- > | org-entry-get-with-inheritance is a Lisp function in `org.el'. > | > | (org-entry-get-with-inheritance PROPERTY &optional LITERAL-NIL) > | > | Get entry property, and search higher levels if not present. > | The search will stop at the first ancestor which has the property defined. > | If the value found is "nil", return nil to show that the property > | should be considered as undefined (this is the meaning of nil here). > | However, if LITERAL-NIL is set, return the string value "nil" instead. > `---- > > so that seems to suggest ":var nil" as a way of knocking out all :var > assignments, but doesn't immediately suggest how to knock out on a > per-variable basis. :var a=nil ? (Which otherwise would look for a src > block named "nil") >
But then (I believe) once we implement the multiple inheritance mentioned in your other thread this would no longer work. > >>> Before we proceed with the variable unsetting, could someone provide a >>> motivating example, just to convince ourselves that the extra features >>> are justified? (The conclusion of another message was that the torque >>> script example was more a motivating example for shebang/preamble >>> processing than for variable unsetting.) >>> >> >> Certainly. >> >> 1. taking Rainer's first example, lets say that you want a variable >> specified for all but one code block in a file (maybe that one code >> block is the source of the value of the variable). In this case it >> would be much simpler to specify the variable file-wide, and then >> unset the variable for that one code block. > > Agreed. It's not clean, but currently in this situation one could just > set the offending variable to some other value. > >> 2. say you want the same session for /nearly/ every code block in a >> file. >> 3. same for :dir, :file, or :shebang... > > I'd just note that some of these already have natural values that can be > used to "unset" > > :session none > :dir . > :shebang "" > > :file <not sure about this one, but maybe "none" should be used...> > So the question seems to be, do we pick some /magic/ values for :var and :file, similar to "none" for sessions, or do we unify this unsetting behavior into a single magic value that can be used to unset any header argument. The later seems cleaner to me. Best -- Eric _______________________________________________ Emacs-orgmode mailing list Please use `Reply All' to send replies to the list. Emacs-orgmode@gnu.org http://lists.gnu.org/mailman/listinfo/emacs-orgmode
