Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#1

Post by tonyonodi » Mon, Jun 30, 2025, 8:10 AM UTC

I launched NumPad v1 on here a few years ago, and back then it wasn't much more than a thin CodeMirror wrapper around the calculator engine I'd written.

Now I've rewritten it as a PWA that supports multiple documents, persists them to IndexedDB, and has a syncing service for paying customers. Syncing is handled by Automerge[1] under the hood, which should make it relatively easy to get document sharing working too.

[1] https://automerge.org/

Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing
numpad.io

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#2

Post by johncosta27 » Mon, Jun 30, 2025, 10:57 AM UTC

This is very cool. I was able to so some a small budget to see what my expenses are monthly, it's quite nice. I can see myself using it anytime I need something more than paper, and less than a full spreadsheet. Very cool.

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#3

Post by eps » Thu, Jul 03, 2025, 11:18 PM UTC

johncosta27 wrote: post #2

This is very cool. I was able to so some a small budget to see what my expenses are monthly, it's quite nice. I can see myself using it anytime I need something more than paper, and less than a full spreadsheet. Very cool.

[flagged]

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#4

Post by jasonjmcghee » Thu, Jul 03, 2025, 11:33 PM UTC

eps wrote: post #3

johncosta27 wrote: post #2

This is very cool. I was able to so some a small budget to see what my expenses are monthly, it's quite nice. I can see myself using it anytime I need something more than paper, and less than a full spreadsheet. Very cool.

[flagged]

Clearly he likes notepad calculators.

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#5

Post by wslh » Fri, Jul 04, 2025, 12:34 AM UTC

Looking for other notepad calculators I found odd products like this: https://www.ubuy.com.ar/en/product/IP17JM9X0-calculator-with...

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#6

Post by abfar » Fri, Jul 04, 2025, 1:48 AM UTC

Nice tool, but the calculator executes division before exponentiation. E.g. 2^4/2 is evaluated to 4, not 8. However, it executes exponentiation first before multiplication (e.g. 2^2*3 is evaluated to 12). Is this intentional?

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#7

Post by kragen » Fri, Jul 04, 2025, 1:57 AM UTC

That's pretty nice; I've made a few attempts at such things myself, but the UI flow seems pretty smooth.

What's the license? I wouldn't want to use your code if copyright law poses a threat.

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#8

Post by kragen » Fri, Jul 04, 2025, 1:58 AM UTC

jasonjmcghee wrote: post #4

eps wrote: post #3

Earlier quoted context omitted.

[flagged]

Clearly he likes notepad calculators.

Was the other one by a different author?

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#9

Post by ajjenkins » Fri, Jul 04, 2025, 2:14 AM UTC

This is really cool. I’m not sure what I would ever use it for, but it’s a cool idea and seems well executed.

Re: Show HN: I rewrote my notepad calculator as a local-first app with CRDT syncing

#10

Post by bobeboph » Fri, Jul 04, 2025, 2:34 AM UTC

abfar wrote: post #6

Nice tool, but the calculator executes division before exponentiation. E.g. 2^4/2 is evaluated to 4, not 8. However, it executes exponentiation first before multiplication (e.g. 2^2*3 is evaluated to 12). Is this intentional?

This is intentional, even if unexpected, as shown in line 152 of the link (turn on line numbers in the settings menu). I agree that following PEMDAS would make more sense.

Edit: it's the equation below "Although if you want to find roots higher than 3..."