You sound just like me of about 12 years ago!

I remember thinking: "I keep reading all this stuff about how Lisp is so much better than all of the popular languages I know about, so is it going to start taking over soon? Is C++ about to go the way of the dodo?"

12 years later, C++ is still around and about as dominant as it was 12 years ago. So I guess the first thing I'd say is: PL enthusiasts on the Internet are not the best indicator of what's about to get big. My best explanation for this is: PL enthusiasts have a somewhat different set of values and aptitudes than mainstream programmers:

- a PL enthusiast is willing to invest a lot of effort into learning and using a language/tool that they think is better. Mainstream programmers will usually go with what has a lot of momentum and support.

- a PL enthusiast usually has a knack for thinking very abstractly, so what looks elegant to them will often be very difficult for less abstract thinkers to unpack.

- a PL enthusiast is usually more concerned with making a language fit an elegant mathematical model than making it fit the model of the underlying hardware.

So PL people end up loving languages like Lisp or Haskell because they are much "cleaner" from a mathematical/abstraction standpoint (particularly in how they eliminate or tightly control side effects). And even though the mathematical models aren't very close to how the hardware works, people have invested a lot of work into making the compilers optimize things so that they are often very efficient -- comparable to what you'd get if you wrote things in a much more "manual" way in an imperative language.

However, because there is a lot of transformation that happens in the compiler, it can be very hard to predict how efficient the program will actually be. You're sort of at the mercy of the compiler -- it can completely change the big-O in both time and space! So while the language itself gave you an elegant way to say something, you may have to get your head around the language's evaluation model and optimizations before you can understand why it has the performance characteristics it does.

For example, one time when I was trying Haskell I wanted to know if a trivial function I wrote took O(1) or O(n) memory. The people on the Haskell list were very helpful, but look how much analysis it took just to answer this simple question!

http://www.haskell.org/pipermail/glasgow-haskell-users/2009-...

But languages like Lisp and Haskell are still highly valuable even to the "mainstream" in that they explore a lot of powerful and abstract concepts, and these feed into more mainstream languages. 10-15 years ago few mainstream languages had "lambda" (from Lisp), now most mainstream languages do (JavaScript, Ruby, Python kinda, Java, C#, even C++). Algebraic datatypes (from Haskell) are showing up in Rust. So I think of Lisp/Haskell as idea incubators that make powerful features a lot easier to add to more mainstream languages, because Lisp/Haskell have already tried them out and run into all the questions and edge cases around them.

So now your next question: why all the new languages, and will any of them take off?

New languages are exciting when they can open up new possibilities. But the downside is that languages have strong "network effects" -- integrating different languages together is a pain. Languages succeed when the plusses of the new possibilities outweigh the inherent costs of using a new/different language.

You listed a lot of languages but the main one I want to talk about is Rust. Rust opens up a huge new possibility: the possibility of getting memory safety without giving up performance or control. No mainstream language has ever done this before.

Traditionally you have had two choices. Either you get top performance and control with a memory-unsafe language (C, C++) or you get memory safety while tethering yourself to a garbage-collecting runtime (Java, C#, Python, etc).

(People will come out of the woodwork here to argue that their favorite GC'd language is faster than C and C++ on their favorite benchmark. Such benchmarks usually tend to be a bit fishy, but this is beside the point. The point is that C and C++ give you the control to do whatever the other language might have done to beat you. Other languages winning is just a local maximum, in which the C or C++ programmer has not yet optimized their program to win. The reverse is not true: when you are tethered to a garbage-collecting runtime, there are certain behaviors built-in that you simply cannot work around).

What makes Rust exciting and very new is that it gives you the best of both worlds. Rust is memory-safe (except in localized "unsafe" blocks), but does not impose any kind of runtime or GC onto you. This could completely change the way that we write performance-critical software.