The Adoption Formula
Over at the Arc Language Blog, there's a nice post trying to give a reason why cool new technologies like Haskell don't catch on nowadays - and why cool old technologies like Lisp didn't catch on some years ago. I'd toss in some Prolog, too - although one reason for Prolog not to be adopted was surely that it was a pain to run on olden days machines.
What they say, basically, is that languages like Lisp or Haskell (or Prolog) are solutions in search of a problem. Not that they're not cool. They are. But who needs higher order functions in programming?
The basic problem is a relation between a certain user's crisis (set of problems, if you so prefer) and the pain of adoption. Let's face it: programmers are a lazy bunch. We'll try not to deviate from the known path any more than we absolutely have to. We remember what a pain it was getting here in the first place. So we have to have a big crisis and some solution that can easily solve this crisis by offering us a way to approach our problems that feels similar to what we already know. Since Haskell, Lisp and Prolog all offer solutions to a set of problems most programmers are not even aware they have (and therefore probably don't really have in the first place), not many people bother picking them up. If they offered solutions to problems programmers know they have, they would see a wider range of adoption.
To make it a bit more clear, take Linux as an example. When Linux saw the light of day, there was an operating system crisis of some sort: Windows dominated the markets and UNIX-based solutions for home PCs weren't cheap or viable (or at all available). BSD was closed source, the HURD was the same vapor it's today. Linux offered UNIX-geeks an easy way out: an operating system that's the same in many aspects, except for those that weren't good about the old one. So that's why Linux got big in geek-world.
But on the desktop market, where grandma and all those pathetic stereotypical example PEBKACs can't tell the difference between a browser and a mail application, Linux is still largely unheard of. Why? Well, Linux solves problems grandma doesn't even know how to spell, nevermind realise having them. Free software? DRM? Hardware support? Stability? Security? Who cares?
Spinning 3D cube? Oooooh, shiny!
That's All Folks... is it?
I'd argue that there is one more aspect to it: if technologies like Lisp or Prolog didn't get adopted, why are they not forgotten? Heck, even COBOL is still around and COBOL is everything but cool. There's an easy answer: those languages found a niche. Lisp has always been big in AI development. COBOL, who knows. Prolog has always had a nice and warm room in the basement of universities - and is now catching on in NLP. In those niches, people come from a different background. They have a different notion of pain. For me, managing pointers, malloc() calls and machine code are a pain. I can deal with the first, don't really understand much about the second and have an allergy to the third. But higher order functions? I've had dreams which happened in intensional logic (that was after reading a paper by Groenendijk & Stokhof, I think)! That was a weird feeling waking up, I can tell you.
Also, our crises are different: we need to interface with inferencing tools, and translate logic and mathematical formulae directly into machine instructions. Doing this in C is a pain. I have nothing but admiration for the people behind prover9/mace4, but I'd argue that Haskell is more suitable for that task. A solution that is less of a pain for us is Prolog. You can program almost the same way you write things down in theory (and quickly see where your theory is failing. Damn). You can then go on debugging your theory and back again to punching it in. To a person doing work in IT business, Prolog will look like a complete disaster. What, no unit tests?. Well, no. But you have guitracer/0 :-).
So, I don't think that Prolog has to catch on. It's good enough if it stays around. Haskell is more suitable for an even wider range of tasks (basically everything), but probably even more of a pain to get started with. But it seems that recently many people got interested in Haskell. The Programming Reddit is full of Haskell lately. And there is now a haskell-beginners list and it seems that introductory CS courses at Tübingen University are being taught in Scheme. Functional programming has received a lot of attention lately - let's see what comes out of it.
Meanwhile, I don't care. As long as Haskell and Prolog continue to be developed and used by a certain niche population, I'm happy. I'll be using them happily. They solve some crises I have, they are not a big pain to adopt if you come with a strong background in logics and sorted type theory. And every time I cuss at Prolog, I have to remember: would it be any better doing this in Java? Probably not.
Oh, and by the way: if you happen to wonder what good books there are on learning logic: Read Gamut's Introduction to Logic and also Volume 2, Introduction to Intensional Logic. Some of the best books I've ever had the pleasure to read. Somewhere next to Camus' Stranger, Dostojewski's Idiot and Nietzsche's Zarathustra.