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Comment by bitcracker | Hacker News Reader

It amazes me how programming languages and APIs look more and more like Lisp. Modern languages copy essential features from Lisp, and JSON as one of the most popular JS libs almost look identical to Lisp s-expressions.

Someday also more people will realize how useful and effective the equivalence of control structures and data really is.

JSON: { "posts": { "id": "1", "title": "Rails is Omakase", "rels": { "author": 9, "comments": [ 5, 12, 17, 20 ] } } }

LISP: (posts (id 1) (title "Rails is Omakase") (rels (author 9) (comments (5 12 17 20))))

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Yeah. Well. Also known as "in the end, everything is just an abstract syntax tree". But while a few people will always delight and excel in reading and writing everything as s-expressions, many of us will probably always find either line-breaks or different kinds of braces, brackets and little syntactic doodads make for easier and saner writing and reading -- even if the parser needs to do a bit more work.

No matter what kind of code I'm looking at: "could I express this as s-expressions?" Sure. "Would I want to?" Hell no.

> "could I express this as s-expressions?" Sure. "Would I want to?" Hell no.

Of course it is possible to implement syntactic sugar in Lisp which supports JSON style expressions. DSLs are common in Lisp, and that actually became a weakness of Lisp (so-called "DSL hell").

The interesting thing about s-expr is that Lisp doesn't need special data conversion tools to handle them. Even control structures are expressed as s-expr, and they can be created and modified dynamically which means that even code can be exchanged at runtime on the fly.

This is one of the most attractive things of lisp. The fact that the language has no notion of compiletime, evaltime and runtime. The user just doesnt have to care abouut it. Very powerful

This actually isn't true for Common Lisp.

There is a distinction between reader macros and compiler macros, for example, which is relevant for allowing using special syntax be optional for end users.

Certain things also need to be defined if you want them to be available in the compile-time environment. And, sometimes you have to do a bit of extra work if you want to have literal objects in your compilation environment and pass them to runtime.

Check out http://www.lispworks.com/documentation/HyperSpec/Body/03_bc.... though it will probably take you a few readings to make sense of it; I know it did for me.

But for the most part things happen automatically.

Everyone says that, but the thing I loved most about dabbling in elisp was how much nicer things become when your text editor works at the s-expression level. Moving around and manipulating a lisp program is just plain easier than it is in nearly any other language.

> easier and saner writing

No. Just no. I could agree about reading, but writing is much easier with s-exps. There's just less symbols to type. And remember, you still can put newlines and indent however you want.

It's JavaScript, that's the syntax notation for JavaScript objects. Sure it resembles lisp and python, but that's just how languages come to be. If I were to invent a new language, if likely use {} for dictionaries and [] for lists too.

Lisp is harder to read than JavaScript because it doesn't disambiguation between lists and dictionaries in a clear way like js and python do.

I think it's more about the tree data structure than about LISP. LISP just makes the underlying data structure obvious, but as you implied we are far from seeing any LISP-semantics in JS(ON).

Or in Rebol:

  [posts: [id: 1 title: "Rails is Omakase" rels: [author: 9 comments: [5 12 17 20]]]]

See relevant|related|interesting blog post On JSON and REBOL by Carl Sassenrath - http://www.rebol.com/cgi-bin/blog.r?view=0522

S-exps are "just" data structures, so that you are reading s-exps when you see other data-structures presented is no surprise.

This is easy to identify: nearly all json is just atoms thought- very few json definitions encode any kind of machine-works or program-code.

So, to put it another way: it amazes you how all Lisp looks like data structures. And hopefully I've helped let you know why you are so amazed here, thanks for reading.

Or in Clojure:

  { "posts" { "id" "1", "title" "Rails is Omakase", "rels" { "author" 9, "comments" [ 5, 12, 17, 20 ] } } }

Commas are unnecessary, I kept them for clarity.

I'm not sure I like this syntax. It's unfamiliar both to lispers and "mainstreamers". The former will be irritated with { and commas, the latter will try to insert : everywhere.

I read an interview with Rich Hickey where he said that adding these three syntax constructs reduced cognitive burden on programmers. He meant () for lists, [] for vectors and {} for hashes.

I should implement it in Racket and just see how it feels.

There was a discussion on the mailing list concerning colon in maps, here's the JIRA issue [1]. IIRC it was kind of decided to let it die, but maybe someone will implement it.

Personally I think that differentiating between lists and maps is important and the way Clojure does it (as well as JSON) is quite easy to write and read. FWIW example given by bitcracker is broken because there's no way to understand what does the following mean:

   (rels (author 9) (comments (5 12 17 20)))

The outermost element is it a list or a map?

[1] http://dev.clojure.org/jira/browse/CLJ-899

Wouldn't it be better to use keywords here?:

  { :posts { :id 1 :title "Rails is Omakase" :rels { :author 9 :comments [5 12 17 20] }}}

Yes, this is the usual way in Common Lisp.

Relevant:

http://paulgraham.com/icad.html

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