The following post is written because people voted that they wanted to read it. Please try to avoid standards "you are wrong because X". If you want to debate, explain instead what's so great about a language that it makes it worth it for me to use it anyway.
Programming languages I have a problem with for various reasons:
Python: I don't like this one because it's rather poorly designed, and its implementation isn't great (I had to work on its code base some number of years ago, and I was surprised how poor the code was). It's also very slow. Add to this the significant whitespace, which deserves a post of its own, and we have a language which truly is the Visual Basic of this century.
C++: Overengineered. Individual features on their own sound very nice when described, but here we have a language which is truly worse than the sum of its parts. I believe that C++ is never the best choice of language when starting a project.
Swift: NIH project by Apple. This language has single-handedly convinced a generation of developers that reference counting is somehow better than garbage collection.
PHP: Well, it's just terrible. There is not that much need to bash it though, because people seem to be moving away from it.
Rust: I actually don't think the language is bad. But a lot of their fans leave something to be desired.
Go: The "trust us, we know better than you" attitude of the language design is enough to be put off by it. Forced code reformatting? Static linking only? No generics because the designers feel that pepole can't handle it?
Kotlin: I actually like Kotlin quite a bit. I used to do a lot of Java, and Kotlin has some really nice features. However, it could be so much more if the designers wasn't so stuck in the notion that it has to be a natural feature for the JVM (making, for example, multimethods difficult). They have also raised the same reasons as the Go designers when advanced features are suggested. Now it's mainly just a Java with better syntax.
Lua: Uses 1-based arrays.
C#: I haven't looked at it for a very long time. Back when I did, coming from Java, I really didn't like the fact that its syntax was the Microsoft code style applied to Java. But beyond the code style, applications written in it really only feels at home on Windows, and since I don't use Windows when doing personal development, there is not much reason for me to look at this further, even though I have heard it's improved a lot.
@shapr I don't actually have that much experience with either, but the little I have had has been mostly positive actually. I think the reason for this is that I haven't simply used them enough to discover in what ways they are bad.
Note, however, that my positive impression of Haskell is on the theoretical level. I find the idea of doubling down on the pure-ness of a functional language to be interesting in the same way I find Unlambda very interesing. It's a great way to understand the ideas behind functional programming.
As a practical language however, I'm not so rigid in my views on functional programming that I'm not willing to sacrifice some mutability here and there in order to be able to write real code.
And yes, I believe monads are, despite their solid theoretical underpinnings, just a hack. It's similar to my idea that I can make C into a pure functional language as long as I pass a state object to every function call (where the state object represents the state of the entire memory of the machine).
Using different languages for describing, theming, and coding the logic of a UI is somewhat better than mixing everything into a single language. Reusing the rendering engine of a web browser to draw the UI is not a bad idea.
Using node.js as the backend is more questionnable though, as you could have achieved something similar by extending or changing the web browser bindings for local pages.
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