Comment by airstrike
3 days ago
> Maintaining a dependency graph would give us the most efficient updates, but it’s often an overkill for a spreadsheet.
It's not overkill at all. In fact, it's absolutely necessary for all but the simplest toy examples.
Isn’t the existence & success of visicalc a direct counter to this?
> Since the formulas did depend on each other the order of (re)calculation made a difference. The first idea was to follow the dependency chains but this would have involved keeping pointers and that would take up memory. We realized that normal spreadsheets were simple and could be calculated in either row or column order and errors would usually become obvious right away. Later spreadsheets touted "natural order" as a major feature but for the Apple ][ I think we made the right tradeoff.
It would seem that the creators of VisiCalc regarded this is a choice that made sense in the context of the limitations of the Apple ][, but agree that a dependency graph would have been better.
https://www.landley.net/history/mirror/apple2/implementingvi...
Edit: It's also interesting that the tradeoff here is put in terms of correctness, not performance as in the posted article. And that makes sense: Consider a spreadsheet with =B2 in A1 and =B1 in B2. Now change the value of B1. If you recalc the sheet in row-column OR column-row order, B2 will update to match B1, but A1 will now be incorrect! You need to evaluate twice to fully resolve the dependency graph.
Even LaTeX just brute-forces dependencies such as building a table of contents, index, and footnote references by running it a few times until everything stabilizes.
3 replies →
Is anyone using visicalc today? I'm not sure how its past success, however fantastic, can be translated into "a dependency graph is often an overkill for a spreadsheet"
visicalc was rewriten in the 80's for computers newer than the apple ][, so are you asking specifically about the original implementation or later implementations? it makes a difference and mostly disobviates the question.
A still-very-common use case for spreadsheets is just to manage lists of things. For these, there are no formulas or dependencies at all. Another is simple totals of columns of numbers.
There are many common spreadsheet use cases that don't involve complicated dependency trees.
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The clause "it's absolutely necessary for all but the simplest toy examples" is what I was disagreeing with. But I wouldn't be surprised to hear that visicalc adopted one as soon as it was technically feasible in later versions.
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It absolutely is, it's bizarre seeing HNers crapping over approaches used by one of the most successful products in history (Visicalc was literally a system seller) as a "toy" approach.
In 1979!