Dark is good for making backends that need to speak HTTP, store data, do work in the background, and talk to 3rd party APIs. However, Dark is still young and isn't applicable for all tasks just yet.
Dark is really good for building web applications, APIs, and things that speak HTTP. Dark is not intended to be usable for embedded systems, to run existing applications in existing languages, or for code that needs to be extremely high performance.
Similarly, Dark does not have support for many use cases such as bitcoin/crypto, AI/big data, image or video manipulation. If you need a specific library (such as TensorFlow or ImageMagick), you can set up your own service (or use an existing vendor) that supports that library, and then call it from Dark over HTTP, but we do not support these libraries natively in Dark.
Know what you're building
We've found that people who come to "try out" Dark usually don't have a good experience. Dark—like many languages, editors and frameworks—can be quite frustrating at times, and people who try to do things that Dark doesn't do well usually give up. People who succeed typically have a particular web app that they're trying to build.
People who give up typically try to solve Project Euler problems or just poke around - if you do that, you'll probably get bored and move on pretty quickly.
Dark currently does a good job for limited scale applications. We would not feel comfortable with applications with intense spiky loads (such as "daily deals" sites), with a lot of fan-out (social networks), with high bandwidth requirements (streaming video). We currently feel comfortable supporting sites with consistently 10 req/s or fewer (approximately 20M requests per month per site).
Dark has collaboration, but it doesn't scale particularly well yet. People have usually been successful with 2-3 person teams, but not much more than that. We don't yet support "Pull request" style collaboration, nor do we currently have checkpoints in our version control, making it currently unsuitable for the kind of collaboration that is needed for larger teams. We intend to add support for these over time.
Limited package manager
We recently released our package manager, but currently only Dark employees can add packages. Right now, you can use 3rd party APIs directly using the HttpClient module. We are working to allow user-contributed packages, which should significantly increase the number of 3rd party APIs that we directly support (such as Stripe, Twitter, Twilio, GitHub, etc), and expect to support them in Q3 2020.
All of our packages are currently built on JSON/HTTP, and so we do not yet support Thrift, GRPC, or GraphQL. We expect to support these in the future.
Dark is a large project, and part of where we've cut scope is on the language
definition. A lot of the Dark language is incomplete, but we believe there is
enough there to build most web applications. Some examples: Dark is strongly
typed, but it doesn't have a full type-checker; we don't support tuples or
character literals; you can't type a negative number in our editor (though you
0 - number as a substitute). As we grow, we'll grow
the language with it, and we believe we have a path for Dark to be a powerful,