What is the appeal of LISP? [on hold]

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Category:Languages

As the title says, what's the appeal of LISP?

I've seen it raised to high heavens and back and then put on a pedestal over an over. I've seen it done by by people here, by actual programmers that I know, by university professors that try to look like the kind of enlightened guys who have obviously transcended the plebeian language-war and would rather die than commit the heresy of saying that one language is better than another.

I tried to learn it, I looked at a few tutorials, at the "learn x in y minutes" page for both lisp and clojure(since from what I understand it's lisp running on the jvm with more FP thrown in), and I understand the syntax and how to do stuff in it. And I went back to tutorials about it several times over the last few months but every time the syntax made me want to look for a high-school kid and yell at him for messy code because looks like a C-style if-condition gone wild with all the nested parentheses and simple things seem to become a chore. What lisp seems to do in a few lines, other FP languages like Haskell or F# or even non FP languages like C# who just discovered that map and filter are a thing seem to do in much less in a much more expressive way.

Am I looking at this wrong? Is there some click that needs to happen? Did I only find crappy resources?(if yes please give me some good resources for learning lisp/clojure, preferably with some exercises)

What in the ... is the appeal of lisp? Honest to God question here.

Thank you in advance!


When I first heard about Clojure in 2009, I wrote a blog post titled "Clojure: Where's the Elegance?" I was a big fan of Python's style of elegance at the time ("executable pseudo-code"), and Lisp was deeply unfamiliar. I continued wrestling with Clojure, though, because "list processing" seemed like an important programming paradigm to have in my toolset. I used a lot of JavaScript, Ruby, and C# for a while, and on my own time played with ClojureScript. When I finally came back to Python in 2017 to do some data-munging, I discovered I was writing a lot of Clojure-inspired functions to help. Finally, I just started writing the data-processing in Clojure, and I wouldn't go back. So while you've asked a question that may not be answerable, perhaps I can shed some light on what accounts for the difference between your perspective and the enthusiasm of the Lisp community.

First, while Lisp is very alien coming from the rich grammars of C, Python, and Ruby, the lightness of Lisp's syntax turns out to be a tremendous blessing. It relieves a lot of cognitive burden. Many kinds of syntax errors completely disappear. But by far the most good I get out of Lisp's consistent grammar is how easily it can be transformed. What I miss most when working in other languages is the ability to rearrange the AST without having to fiddle with the actual text of the code. Working with Lisp is far more fluid than any other language I've experienced.

Second, it's trivial to control how code is evaluated. A lot has been written about the glory of macros, but to me the fundamental superpower is that you can prevent code from being evaluated, evaluate it in a specific order, or evaluate it multiple times, all without the syntactic overhead of wrapping that code in a function. That said, I don't write macros very much, but when I do, a function is a poor substitute.

Third, most languages don't have very good support for live coding. I typically don't use the REPL itself, but rely on an editor integration to evaluate code. Clojure's tooling is good enough that I can mold an entire codebase with dozens of namespaces without ever having to restart the JVM process or split a single big code file into separate modules.

Fourth, Lisp code tends to compose extremely well. Between everything being an expression that returns a value and the language being built on a relatively small set of data structures, you can mix and match language constructs with great liberty. That opens up a lot of possibilities where other languages put up walls.

The common factor of all these is that the language does its best to get out of your way. When I was a novice programmer, the complex grammars of C and Python and Ruby was an aid to programming. It kept me on the straight and narrow. The language constructs were like landmarks to navigate by. Lisp, without those landmarks, can feel like a foreign country. But as you get more familiar with Lisp, other languages feel artificially constraining and hard to move around in, like driving on roads when you could be flying. Lisp is very freeing, but from my personal experience, I can tell you that, like flying, it takes practice before the strangeness of it turns from fear to freedom.

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