lager VS clojure

observer: I changed how observer<> works, this is basically a template-class which observes a value and then calls a registered callback on modification. It can now create a sub-observer<> from a member variable of the value it observers. This makes it possible for widgets to be composable. This is based loosely on lager's lenses and cursors.

By using arximboldi/lager

My preferred approach is to abstract things so the boundary between the objects is not a function call, but a value being passed. This was shown to me the first time via Boundaries (from Gary Bernhadt). In C++ world, the talks from Juan Pedro Bolívar Puente are great, as he also is the author of a framework to structure applications that way, the framework is open source, and it's been used in production applications, probably using Qt as well. I would start by watching The Most Valuable Values and Squaring the Circle. If you prefer text, go read Lager's excellent documentation.

I like working in C++, after a decade of working in Java, Python, Javascript and Clojure, I find working in C++ (which I learned before these other languages) to be quite fun and pleasant, at least with relatively modern C++.

I've been, on and off, working on a little toy game engine, for a few years. Its a mix of keeping up with C++ advancements, learning various concepts like physically based rendering, and just the fun of crafting a big project, with no constraints other than my time and ability, no deadlines, no expectation of releasing anything. Its cathartic and enjoyable. I really do enjoy it.

Last September, I got frustrated with something I was working on in a more serious capacity. It was some server software, it responded to HTTP requests, it accessed third party services over HTTP and Websockets, it talked to a Postgres database. Overall it was an event driven system that transformed data and generated actions that would be applied by talking to third party services. The "real" version was written in Clojure and it worked pretty well. I really like Clojure, so all good.

But because I was frustrated with some things about how it ran and the resources it took up, I wondered what it would be like if I developed a little lean-and-mean version in C++. So I gave it a try as a side project for a few weeks. I used doctest[1] for testing, immer[2] for Clojure-like immutable data structures, [3] lager for Elm-like application state and logic management, Crow[4] for my HTTP server, ASIO[5] and websocketpp[6] for Websockets, cpp-httplib[7] as a HTTP client and PGFE[8] for Postgres, amongst some other little utility libraries. I also wrote it in a Literate Programming style using Entangled[9], which helped me keep everything well documented and explained.

For the most part, it worked pretty well. Using immer and lager helped keep the logic safe and to the point. The application started and ran very quickly and used very little cpu or memory. However, as the complexity grew, especially when using template heavy libraries like lager, or dealing with complex things like ASIO, it became very frustrating to deal with errors. Template errors even on clang became incomprehensible and segmentation faults when something wasn't quite right became pretty hard to diagnose. I had neither of these problems working on my game engine, but both became issues on this experiment. After a few weeks, I gave up on it. I do think I could have made it work and definitely could go back and simplify some of the decisions I made to make it more manageable, but ultimately, it was more work than I had free time to dedicate to it.

So my experience was that, yes, you can write high level application logic for HTTP web backends in C++. You can even use tools like immer or lager to make it feel very functional-programming in style and make the application logic really clean. Its not hard to make it run efficiently both in terms of running time and memory usage, certainly when comparing to Clojure or Python. However, I found that over all, it just wasn't as easy or productive as either of those languages and I spent more time fighting the language deficiencies, even with modern C++, than I do when using Clojure or Python.

I think I would think very long and hard before seriously considering writing a web backend in C++. If I had the time, I'd love to retry the experiment but using Rust, to see how it compares.

[1] https://github.com/doctest/doctest

[2] https://github.com/arximboldi/immer

[3] https://github.com/arximboldi/lager

[4] https://github.com/CrowCpp/crow

[5] https://think-async.com/Asio/

[6] https://www.zaphoyd.com/projects/websocketpp/

[7] https://github.com/yhirose/cpp-httplib

[8] https://github.com/dmitigr/pgfe

[9] https://entangled.github.io/

This article will explain how to write a simple service in Clojure. The sweet spot of making applications in Clojure is that you can expressively use an entire rich Java ecosystem. Less code, less boilerplate: it is possible to achieve more with less. In this example, I use most of the libraries from the Java world; everything else is a thin Clojure wrapper around Java libraries.

5. Clojure - $96,381

I have a tangential question that is related to this cool new feature.

Warning: the question I ask comes from a part of my brain that is currently melted due to heavy thinking.

Context: I write a fair amount of Clojure, and in Lisps the code itself is a tree. Just like this F# parallel graph type-checker. In Lisps, one would use Macros to perform compile-time computation to accomplish something like this, I think.

More context: Idris2 allows for first class type-driven development, where the types are passed around and used to formally specify program behavior, even down to the value of a particular definition.

Given that this F# feature enables parallel analysis, wouldn't it make sense to do all of our development in a Lisp-like Trie structure where the types are simply part of the program itself, like in Idris2?

Also related, is this similar to how HVM works with their "Interaction nets"?

https://github.com/HigherOrderCO/HVM

https://www.idris-lang.org/

https://clojure.org/

I'm afraid I don't even understand what the difference between code, data, and types are anymore... it used to make sense, but these new languages have dissolved those boundaries in my mind, and I am not sure how to build it back up again.

As an analogy - my face hasn't changed all that much in a past few years, and I haven't changed my profile picture in those few years. Does it really mean that I'm unmaintained/dead?

> Where can I find latest documentation [...]?

The answer is still https://clojure.org/. And https://clojuredocs.org/ but it's community-maintained so might occasionally be missing some things right after they're released. E.g. as of this moment Clojure 1.11 is still not there since the maintainer of the website has some technical issues deploying the updated version of the website.

For me personally, the best API-level documentation is the source code.

> Where can I find [...] tools / libraries in a easy to use page or section?

There's no central repository of all the available things since they can be loaded from many places (Clojars, Maven Central, other Maven repositories, S3, Git, local files).

But there are community-maintained lists, like the one you've mentioned at https://www.clojure-toolbox.com (fully manual, AFAIK) or the one at https://phronmophobic.github.io/dewey/search.html (automated but only for GitHub). Perhaps there are others but I'm not familiar with them - most of the time, I myself don't find that much value in such services as I'm usually able to find things with a regular web search engine or ask the community when I need something in particular.

They are written in Java, and implement a bunch of interfaces, so the implementation looks complicated, but they are basically just classes with head and tail fields.

https://github.com/clojure/clojure/blob/master/src/jvm/cloju...

Like this.

As a Java/Scala user you should check out Clojure! It is highly recommended (https://clojure.org)

Lisp is not a programming language, but a family of languages ​​with many dialects. The most famous dialects include Common Lisp, Clojure, Scheme and Racket. So after deciding that I was going to learn Lisp, I had to choose one of its dialects.

I learned Clojure to implement a plugin for Metabase (the tool my former company used for creating business dashboards). I probably won’t ever use the language anymore in the future, but learning functional programming was fun and eye-opening.