[nhatcher]

> Do you use cached calculation chains for performance optimizations?

Not yet, there is heavy research in that direction. I will write on this soo-ish

> Do you take volatile functions into account?

Yes, for instance RANDBETWEEN and NOW are implemented. Things like `IF(RANDBTWEEN(1, 500)> 200,A1, A2)` work fine

Thnaks

[8n4vidtmkvmk]

What does that actually mean, "works"? I don't know how that behaves in Google sheets or Excel. Is it evaluated exactly once the first time the formula is entered? Every time you focus the input? Is the dice rerolled when a1 or a2 is modified? What?

[nhatcher]

Hi 8n4vidtmkvmk, the algorithms for evaluating spreadsheets are surprisingly tricky mainly because of the dependencies. The dependencies are only know at runtime and in Excel are lazy evaluated. So things like `IF(condition, value1, value2)` would evaluate first the condition if it is true it will evaluate value1 but not value2. So things that in other programming languages are a circular dependency are not so in Excel. The problem of computing the dependencies might be solved by topological sort. The complication of the runtime dependencies is made worse by having dependencies that change every time (or that their outputs do not dependency solely of their inputs) like random functions or date functions. An optimization while evaluating a spreadsheet would be to only compute those cells that depend on cells whose value changed. If you do that you might miss on those volatile functions.

I realize I am most likely babbling too much.

Yes, volatile functions like RANDBETWEEN get evaluated each time a cell changes. They don't get evaluated when you focus on them.

[8n4vidtmkvmk]

Thanks. I wonder if it would make sense for RANDBTWEEN to take a seed so that it becomes non-volatile unless you use time as the seed.