[hahooooo]

Is there any advantage in using a functional language when programming non-mathematically related code?

I see how it can help write Neural Networks, AI, financial code, etc. But if you know Python,Ruby,PHP,Java and Lisp (well), why would you choose to write a blog, webstore, webmail client or social media* app (which probably is about 90% of what people actually do) in Lisp over the four three?

I'll tell you why I would chose the first four:

1. Large community. 2. Many more libraries. 3. Easier to hire.

*Except for (perhaps) a small spam-block/feed ai module

[nv-vn]

Yes. Functional programming (although it isn't necessarily a trait of Lisp) has, in fact, little relation to math (despite what many people believe). It's also very far removed from the field of AI right now (not for any particular reason, but there's no more specific reason to switch to Lisp for AI than there is for desktop or web apps). The reason you'd use Lisp is quite simple -- it saves time and makes programming easier. Macros are the biggest time saver in the world, and you don't realize how much time you waste writing repetitive code until you get to use them.

As for your 3 reasons in favor of the other languages, I think the first means almost nothing at all. Lisp is much easier (once you grasp it) than many other languages, so I think the fact that you'll get less answers on StackOverflow is irrelevant. As for the second reason, as long as you have one library that works for what you want -- say some library for writing web servers -- it doesn't really matter after that. There's rarely any reason to reinvent the wheel here, and there's always someone that attempted such a common task before you. Just because you don't have 3,000 different choices like in Java, doesn't mean that you won't find high-quality code for what you need to do (in fact, I'd argue that Lisp code has a much higer quality on average than Java code). As for hiring, I think Paul Graham has already given the best comments on this. Simply put, a good programmer can be taught to write good Lisp, even if they don't know it by the time you hire them.

[GlennS]

I'd say web's request -> response model is pretty well suited to functional programming.

It seems popular amongst JavaScript programmers at the moment as well. React, which appears the current hotness, is based on making a functional interface to the DOM.

Although actually, I'd say the main reason to use a Lisp for web gunk is the macros rather than the functional programming. The tree structure maps very naturally onto HTML generation. There are some really nice libraries (in particular I'm familiar with Clojure libraries) which make the server-side part of a web app really neat. You can basically skip the whole 'templating' bit.