Ask HN: What did you build in 2019?

I'll definitely take you up on that offer. Thanks for the feedback, I appreciate it!

I am a classical musician, programming for fun. I found guile scheme about 2 years ago, and I have been writing all my software in it since. Such a nice language to be working in!

I wrote a SRFI (scheme request for implementation) for transducers, which are efficient composable algorithmic transformations. They allow you to eagerly transform collections, say like using map and filter, but without building intermediate collections. The SRFI document is here: https://srfi.schemers.org/srfi-171/srfi-171.html

Then I rewrote a large chunk of racket's for loops for guile: https://hg.sr.ht/~bjoli/guile-for-loops

They are zero cost (apart from negligible macro expansion) and provide a homogenous way to iterate through various collections. I am now in the process of implementing foldr for it, which will allow for a general way of writing lazy iterations.

Completed the model in 2019 ... It took me 22 years to get it right

The biggest thing I have built this year is Hexadecimal (https://tryhexadecimal.com). It is my first SaaS business, so it is a pretty rough endeavor, both on the development and the business side. Built on the vanilla Rails stack. As boring as it could possibly get. I have described in some detail the tech behind it: https://runninginproduction.com/interviews/9-running-a-websi...

Lessons learned:

* If you'd like to start making money on the Internets, don't start with a SaaS

* Making your first $currency will give you a (much needed) morale boost

* If you're just starting out and you're in for the long-term, optimize for learning and building relationships

* Worthwile Things take time

* You probably won't get it right from the first time (whatever it is). It is far more important to keep iterating rather than getting the right answers from the very beginning.

* Most minor decisions won't matter in a few months', let alone in a few years' time. Don't overthink it. Make a fast decision and if necessary, re-evaluate it down the road

* Don't rush to automate tasks

* Build it, and they will do absolutely nothing

* Businesses live and die by their distribution channels

* Running a lean operation (i.e. low-cost) is a competitive advantage

* Having an audience is an unfair advantage

* Writing is a gift that keeps giving. Write more!

* The true validation is people paying you money

After many months (or years?) of procrastinating, I finally published my personal website (https://jmstfv.com). I have been meaning to do this for a long time but kept putting it off for various (artificial) reasons. So, I hand wrote the HTML, copy pasted the CSS from my other projects, and called it a day.

Lesson learned: start with the least painful solution.

EDIT: added couple more "lessons learned"

I released version 9 of Planimeter's Grid Engine, the largest pure Lua game engine on GitHub. https://www.planimeter.org/grid-sdk/