Spreadsheet-style dependency tracking

[Florian Weimer]

* Chris Torek:

> In article <87y69xbz6h.fsf at mid.deneb.enyo.de>
> Florian Weimer  <fw at deneb.enyo.de> wrote:
>>Are there libraries which implement some form of spreadsheet-style
>>dependency tracking?  The idea is to enable incremental updates to
>>some fairly convoluted computation.  I hope that a general dependency
>>tracking framework would avoid making the computation even more
>>convoluted and difficult to change.
>
> Don't know of any libraries myself, but I wrote some code to do
> topological sort for dependencies, which I can paste here.  It
> is also worth noting that a lot of spreadsheets cheat: they just
> repeat a sheet-wide computation until values stop changing (or a
> cycle count limit runs out).

I think most of the relevant implementations use dependency
information to speed up incremental recomputation.  For instance,
gnumeric seems to have code for this.  This is the part I'm most
interested in.  I already have got an explicit ordering of the
computations (fortunately, that part is fairly simple).