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Posted by fouronnes3 5 days ago

Show HN: I made a spreadsheet where formulas also update backwards(victorpoughon.github.io)
Hello HN! I'm happy to release this project today. It's a bidirectional calculator (hence the name bidicalc).

I've been obsessed with the idea of making a spreadsheet where you can update both inputs and outputs, instead of regular spreadsheets where you can only update inputs.

Please let me know what you think! Especially if you find bugs or good example use cases.

250 points | 113 commentspage 4
digdugdirk 3 days ago|
Super cool! Well done. Now take it down and never let Microsoft get their hands on the code, or the entire economic system will go down in flames.
Towaway69 3 days ago|
C-levels have been drawing random lines for years[1] - the invention of the graph let the genie out of the bag.

[1] https://x.com/gothburz/status/1999124665801880032

nrhrjrjrjtntbt 3 days ago||
Excellent (sorry accidental pun)

This is a nice exploration.

aghilmort 3 days ago||
interesting. like Excel Solver? or OpenSolver, Gurobi, other optimizers? or different objective?
fouronnes3 3 days ago|
Never used any of those, so I don't know! I'd be curious to read a comparison from anyone who knows about them.

I think what's pretty unique about the bidicalc solver that I made is that it does not depend on the previous input values to update backwards. It's truly solving the root finding problem. The advantage is that there are never any "stuck in a local optimum" problems with the solver. So you can solve difficult problems like polynomials, etc.

lethal-radio 3 days ago||
What do you use it for?
filipeisho 3 days ago||
set A1 = 3 set B1 = 4

set C1 = A1 + B1 = 7

now change C1 = 14 expected A1 = 6 expected B1 = 8

what it did A1 = 7 B1 = 7

great

fouronnes3 3 days ago|
Why do you think that 6+8 is a better solution than 7+7?
filipeisho 3 days ago|||
When C1 changes from 7 to 14, that’s a scalar change. The least-assumption, information-preserving update is to scale both inputs by the same factor.
ninalanyon 1 day ago|||
It preserves an implicit relationship, ratio, between A and B.
BSTRhino 3 days ago||
What a neat idea!
yogeshpaliyal 3 days ago||
amazing
TypeDeck 3 days ago||
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NedF 3 days ago|
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