Would you use (a dialect of) LISP for a real-world application? Where and why?

Question

LISP (and dialects such as Scheme, Common LISP and Clojure) haven't gained much industry support even though they are quite decent programming languages. (At the moment though it seems like they are gaining some traction).

Now, this is not directly related to the question, which is would you use a LISP dialect for a production program? What kind of program and why? Usages of the kind of being integrated into some other code (e.g. C) are included as well, but note that it is what you mean in your answer. Broad concepts are preferred but specific applications are okey as well.

Answer 1

Would you use a LISP dialect for a production program?

Absolutely

What kind of program and why?

Lisp is a general purpose dynamic language. Today, it has the same basic difficulties as other general purpose dynamic languages that aren't published by Microsoft: Native threads, GUI integration, deterministic operation of the GC, and small memory footprints.

Native threads are achieved by LispWorks and SBCL, I believe. Possibly others? I have not investigated fully.

LispWorks and Franz Common Lisp - commercial products - integrate into the GUI to degrees of success. Not having the $$ to buy them, I don't know how well it works. I suspect they work quite well...

A deterministic GC operation can be done (it's done in Java to some level of success), but I don't know if existing Lisp systems (maintained ones) have any code to do that.

Small memory footprint I believe is achieved by some Lisps.

My basic point is, Common Lisp is technically ready to make production systems. And it does.

The vast majority of developers get freaked out by (pick one) dynamic languages, macros, parentheses, lack of favorite IDE, bad experience in college, not many jobs in it, and then don't use it.

Personally I'd jump at building a full-fledged production system in Common Lisp from the ground up in a team environment.

edit: I didn't really answer why Lisp as opposed to other languages.

In my Lisp experience - not significant, but considerably more than 'hello world' - I've found the language to be extremely usable after the first "Argh new language" pains. The majority of the language fits together in a very regular and fairly obvious fashion that I don't really find other languages to operate like. Part of this is the merging of expressions and statements. Part of this is the core list datatype. Part of this is the type system. Part of this is the macro system. Don't get me wrong, though, there are pain points. But they don't kick me in the face as much as other languages' pain points.

One simplistic example is Python's length-of-list routine. The Python approach is to call len(mysequence). But, if we think about it, a length is a property of a sequence. So, mysequence.len() is a more appropriate idea. Lisp essentially removes that syntactic distinction. (length thing) is both the function call syntax and the method syntax. Of course, some people find that frustrating and want the syntactic difference. I would rather have the regularity.

edit2: I converted the portion of my MS thesis that runs on the desktop to Common Lisp and it's been a pleasure to work with so far.

Answer 2

I'd use LISP if it was the best choice for the job. Just some things that influence the "best choice":

• vendor support. The LISP implementation we use - if something goes wrong and interferes with our development and thus our deadlines, will the vendor work towards a solution with us?
• library support. What libraries are available? String manipulation, math, data-access, web-servlets (or LISP-equivalents), windowing toolkit, etc... I don't want to have to write this stuff from scratch.
• tool support - How good is the IDE? Solid/stable or flaky? Good editor support? Integrated debugger? If I need to do GUI dev in LISP, is there a visual IDE or do I have to code GUI layout by hand (I hate doing that).
• developer buy-in (I really don't want to have to spend too much time teaching my team-mates a whole new language)

All of these factors are to be considered when deciding if LISP is appropriate for a project. In the corporate world, I have never experienced it.

Answer 3

Absolutely. Paul Graham explains it well.

Answer 4

Where: Emacs is a real-world application that uses LISP.

Why: It was a great way to express the mapping between keystroke and action. It's interpreted and it's fast and it's well-defined and it's simple.

Answer 5

I personally know of people using Lisp in the form of Clojure in a couple of investment banks and startups in London. I've also chosen Clojure as the primary development language for my own startup, so I'm willing to put my money where my mouth is :-)

I've found it to be a very enlightening experience to learn Clojure over the past year (after a lot of experience with Java and C#). Main reasons for this are:

• It has quite a strong emphasis on functional programming (more so than most other Lisps). The author and BDFL Rich Hickey has frequently cited Haskell as one of his inspirations for the language design which means you get things like fully immutable data structures and lazy infinite sequences etc.
• Macro metaprogramming - the Lisp "code is data" philosophy is hard to understand unless you've actually experienced it, but it's one of the reasons Lisps are so expressive and productive. You basically have the power to extend the language to match your problem domain.
• Fantastic support for multi-core concurrency - I actually think Clojure is the best language for concurrent programming right now. See http://www.infoq.com/presentations/Value-Identity-State-Rich-Hickey for an enlightening presentation about this
• Interactive development at the REPL is a great, productive way of building applications. It gives you a real feeling of power to dynamically modify your running application code and programatically inspect live data structures.....

It also seems to be a practical choice for real production use for the following reasons:

• Running on the JVM with very easy Java interoperabilitiy gives you access to all the libraries and tools in the Java ecosystem
• You're running on the JVM which is a tried and tested platform for enterprise applications. Clojure benefits from all the nice JVM features like excellent GC and JIT compilation for free.
• It's a dynamic language by default, which makes it very convenient for development and rapid prototyping with hardly any boilerplate. However you can add static type hints to get pretty good performance where you need it.
• It's a pragmatic and helpful community - the kind of culture where people get things done and the focus is on well designed solutions that solve real problems
• There is tool support in multiple IDEs. I personally use Eclipse with Counterclockwise plugin (because I need the Java integration) but there are plenty of other options.

Answer 6

Both Mathematica and Autocad are based on a dialect of Lisp. I would classify them as 'real world' as well as Emacs.

Answer 7

Absolutely I would consider it. Especially for new development work that had some parallel computing potential. That seems to be a sweet spot for these types of functional languages.

Answer 8

Lisp is one of the best choices for implementing compilers. And, as the use of DSLs and eDSLs is increasing now, Lisp is becoming more valuable. I am using a Lisp dialect for all of my DSL-related tasks.

Answer 9

If someone paid me to, sure.

They'd probably be more interested in paying someone who knows the language though. I've only played with elisp and scheme a few times.

Answer 10

Right now I'm trying to use newLisp as a replacement for Php on my personal web site via the Dragonfly framework. If I can figure out how to get Apache to play nice, I'll use it (the built in web server works very well, but I would much rather work through Apache). And once that happens, I'll use newLisp anywhere I would use Php, because I flat don't like Php and I do like newLisp.

Right now, Clojure isn't a good choice for Android apps, but I know people are working on that. So if that gets figured out, that would be another place to I would use a dialect of Lisp for real world applications... but again, this is because I just don't like Java.

But honestly, I prefer Ruby to Lisp... but this is mostly a matter of community and documentation.