I'm working on turning our statically-typed formula engine -- that we use for Calcapp, our app builder -- into a real hosted solution (as well as a library). I discussed it in July last year (https://news.ycombinator.com/item?id=44702833#44704642) and have been working full-time on the project since the beginning of the year.
I figured "I already have a battle-tested solution, I just need to make it modern and spiffy, build a website for it and see if there's any interest -- in the age of Claude Code, this should be fast work!"
Wrong. Taking an internal library and offering it to others -- complete with documentation and modern tooling -- is an immense project, even with the help of AI agents.
Is there a market for a "formula engine in a box"? I don't know. But I also didn't know whether there would be a market for Calcapp either, and that has supported me working full-time for the past seven years. So I'm willing to take another chance.
I'm a co-founder of Calcapp, an app builder for formula-driven apps, and I recently received an email from a customer ending their subscription. They said they appreciated being able to kick the tires with Calcapp, but had now fully moved to an AI-based platform. So we're seeing this reality play out in real time.
The next generation of Calcapp probably won't ship with a built-in LLM agent. Instead, it will expose all functionality via MCP (or whatever protocol replaces it in a few years). My bet is that users will bring their own agents -- agents that already have visibility into all their services and apps.
I hope Calcapp has a bright future. At the same time, we're hedging by turning its formula engine into a developer-focused library and SaaS. I'm now working full-time on this new product and will do a Show HN once we're further along. It's been refreshing to work on something different after many years on an end-user-focused product.
I do think there will still be a place for no-code and low-code tools. As others have noted, guardrails aren't necessarily a bad thing -- they can constrain LLMs in useful ways. I also suspect many "citizen developers" won't be comfortable with LLMs generating code they don't understand. With no-code and low-code, you can usually see and reason about everything the system is doing, and tweak it yourself. At least for now, that's a real advantage.
I spent years building a compiler that takes our custom XML format and generates an app for Android or Java Swing. Gemini pulled off the same feat in under a minute, with no explanation of the format. The XML is fairly self-explanatory, but still.
I tried doing the same with Lovable, but the resulting app wouldn't work properly, and I burned through my credits fast while trying to nudge it into a usable state. This was on another level.
I like to use Claude Code to write deterministic computer programs for me, which then perform the actual work. It saves a lot of time.
I had a big backlog of "nice to have scripts" I wanted to write for years, but couldn't find the time and energy for. A couple of months after I started using Claude Code, most of them exist.
I'm a co-founder of Calcapp, an app builder for formula-driven apps using Excel-like formulas. I spent a couple of days using Claude Code to build 20 new templates for us, and I was blown away. It was able to one-shot most apps, generating competent, intricate apps from having looked at a sample JSON file I put together. I briefly told it about extensions we had made to Excel functions (including lambdas for FILTER, named sort type enums for XMATCH, etc), and it picked those up immediately.
At one point, it generated a verbose formula and mentioned, off-handedly, that it would have been prettier had Calcapp supported LET. "It does!", I replied, "and as an extension, you can use := instead of , to separate names and values!") and it promptly rewrote it using our extended syntax, producing a sleek formula.
These templates were for various verticals, like real estate, financial planning and retail, and I would have been hard-pressed to produce them without Claude's domain knowledge. And I did it in a weekend! Well, "we" did it in a weekend.
So this development doesn't really surprise me. I'm sure that Claude will be right at home in Excel, and I have already thought about how great it would be if Claude Code found a permanent home in our app designer. I'm concerned about the cost, though, so I'm holding off for now. But it does seem unfair that I get to use Claude to write apps with Calcapp, while our customers don't get that privilege.
I've been using Claude Code a lot lately, and I've been thinking of integrating it into our SaaS tool (a formula-driven app designer). I've been holding off primarily because I've been afraid of the cost (we're not making much money off our $9/mo. customers as it is, and this definitely wouldn't help that).
However, it's becoming clear to me that individual apps and websites won't have their own integrated chatbots for long. They'll be siloed, meaning that they can't talk to one another -- and they sure can't access my file system. So we'll have a chatbot first as part of the web browser, and ultimately as part of the operating system, able to access all your stuff and knowing everything about you. (Scary!)
So the future is to make your software scriptable -- not necessarily for human-written scripts, but for LLM integration (using MCP?). Maybe OLE from the nineties was prescient?
Short-term, though, integrating an LLM would probably be good for business, but given that I'm our only engineer and the fact that our bespoke chatbot would likely become obsolete within two years, I don't think it would be worth the investment.
No, not really. GoRules appears to be a decision engine that allows non-technical users to define rules visually through a graphical interface. Engineers can then interpret and evaluate these rules using provided libraries.
What I'm building is a formula engine that validates, compiles, and evaluates Excel-like formulas. Compared to GoRules, it’s more akin to the ZEN expression language component than to the broader GoRules system.
I'm working on an engine for Excel-like formulas, which will be available both as a library and as a service (which I've mentioned on HN a few times before). I originally started work on the engine back in 2008, when our app builder needed it.
This is a wheel I see people reinventing all the time, often for use in SaaS applications. The implementations are often underwhelming: function support is limited, documentation is sparse to non-existent and errors are typically only communicated at runtime -- if at all. Formula editors usually lack autocomplete, making them frustrating to use.
I've spent years solving all these problems (with a statically-typed language), and I'd love for others to benefit from the work. I have extracted the formula engine from our app compiler, so the library is nearly complete. The runtime part (evaluating formulas) has been rewritten in TypeScript. Next, I'll build a service around it to validate, compile and evaluate formulas -- which should be fun.
I'm planning to do a Show HN once I have a preview up and running.
I know this doesn't add much value to the discussion, but I was really proud of my UIN when I was a teenager. And this may be my last chance to flaunt it, so here it is:
1779900
So back in the day, these were known as Universal Internet Numbers, or UINs. You have to admire the sheer audacity of using that name for the user identifiers of a service you're building. I believe they were renamed to "ICQ#" later.
I figured "I already have a battle-tested solution, I just need to make it modern and spiffy, build a website for it and see if there's any interest -- in the age of Claude Code, this should be fast work!"
Wrong. Taking an internal library and offering it to others -- complete with documentation and modern tooling -- is an immense project, even with the help of AI agents.
Is there a market for a "formula engine in a box"? I don't know. But I also didn't know whether there would be a market for Calcapp either, and that has supported me working full-time for the past seven years. So I'm willing to take another chance.