bidicalc
Dev tools
spreadsheet
SHOW HN2025
252points
116comments
#236of 3,837 in 2025
Top 7%of 2025 by points
How HN took it
CuriousMostly questions and neutral comments
8 positive, 36 neutral or asking, 3 mixed, 13 critical, out of 60 comments about the project. Thread score -0.04.
Idea: 6 for, 6 againstExecution: 1 for, 4 againstDesign: 0 for, 2 againstDocs: 0 for, 1 against
The thread, comment by comment
Each row is a top-level comment and its replies, in HN's order. Select a cell to open that comment on HN.
positive neutral or mixed critical about another commenter or something else the maker
What HN said
What people liked
Clever concept and clean prototype
From 3 comments
Phenomenal! This is a solid prototype, clean execution. I've had exactly this idea, too: I've already given the spreadsheet the relationships between these values, why can't it…
hallole on HNLOL! Gemini suggested to implement this to me literally yesterday: bidirectional computations. The example was that given a temperature in Celsius and Fahrenheit, modifying…
aatd86 on HNExcellent (sorry accidental pun) This is a nice exploration.
nrhrjrjrjtntbt on HN
Similar to Excel goal seek but handles arbitrary input cells
From 1 comment
This is really cool! It's like Excel's goal seek but can also handle the case of arbitrary input cells. Goal seeek can only handle one input and one output cell. But how do you…
thomastay on HN
Objections
Unclear which inputs move when an output changes; needs fixed vs free cells
From 3 comments
The first example on the main page has a formula with two variables being updated from changing one value. The immediate question I have is if I change the output, where does the…
willrshansen on HNThe interesting thing here isn’t “spreadsheet, but backwards” so much as “spreadsheet as a constraint system”. Classic spreadsheets are basically DAGs: data flows one way and a…
pedrozieg on HNThe examples are great and these bidirectional calculators are something that people would love to have in traditional spreadsheets. So much so that Credit Suisse, which…
d--b on HN
Solver fails on some edge cases, such as setting a cell exactly to 100 or multiple outputs at once
From 2 comments
This is great. Since you've asked about bugs, I tried pushing the limits and found the following: ``` A1: 100 B1: =100-A1 A2: =A1*(100-A1) A3: =A1*B1 ``` A2 can be successfully…
penteract on HNset 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
filipeisho on HN
Requests
Ability to mark cells as constants or fixed without special syntax
From 2 comments
I think the concept is solid. I’ve only had a few minutes of playing with it, but I have the opinion is that from a UX perspective constants are more common than variables. So…
kccqzy on HNThe examples are great and these bidirectional calculators are something that people would love to have in traditional spreadsheets. So much so that Credit Suisse, which…
d--b on HN
Domain constraints for variables
From 2 comments
You can do it and it is explained, actually. Use # as a prefix to indicate a constant, e.g.: #50 will be a constant and not a variable. In the future I'd like to support more…
fouronnes3 on HNConstants are supported, use # as a prefix, e.g.; #50. I'd like to add more constraints in the future like a domain constraint for variables.
fouronnes3 on HN
Questions
How the solver chooses among multiple solutions
From 2 comments
I made this mostly as a fun challenge :) You are right that there is some arbitrariness involved when picking a solution, however it's a bit more subtle than that. Let's say our…
fouronnes3 on HNThis is really cool! It's like Excel's goal seek but can also handle the case of arbitrary input cells. Goal seeek can only handle one input and one output cell. But how do you…
thomastay on HN
Whether it can solve inverse kinematics or control problems
From 2 comments
Could you build an inverse kinematics solver with this? (I recently watched a youtube video of someone iteratively working out the solutions for a robotic arm, by alternating…
nico on HNCould this easily represent a Kalman filter and other typically complex control problems? Makes me imagine plotting a inverted pendulum and other real time systems. Could a cell…
koolala on HN
Alternatives named
Excel Goal Seek
From 2 comments
In Excel you have goal seek for this functionality. I believe it does some form of numerical solving of the equation system. Good for every situation when you need to solve…
b-karl on HNThis is really cool! It's like Excel's goal seek but can also handle the case of arbitrary input cells. Goal seeek can only handle one input and one output cell. But how do you…
thomastay on HN
TK Solver
From 1 comment
Wow! See the classic https://en.wikipedia.org/wiki/TK_Solver
PaulHoule on HN
Prolog constraint logic programming (clpr)
From 1 comment
In Prolog you can write rules (similar to functions in other languages) so that they work "both ways". Let's say you have this rule that defines how pace ("runner's speed")…
fainpul on HN
g9 graphics constraint tool
From 1 comment
you might like https://omrelli.ug/g9/ which is a similar concept but for graphics
jy14898 on HN
IBM TM1 and Anaplan break back
From 1 comment
This is pretty cool. This functionality is called ‘break back’ in a lot of enterprise modelling software. See [IBM…
jsax on HN