Lisp isn't difficult to read, so I don't understand the question.

This feels like someone who doesn't know French asking "what makes French difficult to read?"

I'll repeat what other people here have been saying: I don't think Lisp is actually "hard" to read, in any objective sense.

It's "difficult" to read because it's different that other languages, but I think some of those differences actually improve readability once you understand the language. The forced use of parentheses everywhere guarantees that precedence is never ambiguous, for example.

It's the same thing that makes reading Swift code hard if you never worked with it: lack of familiarity.

Unfamiliarity.

You get used to it after a while and at some point the parenthesis 'disappear' and stop taking up mental cycles.

I often thought about this - at first I struggled a lot and wasted so much time trying to match parens, but after some time my brain adapted and then I actually liked the syntax, especially if your editor supports selecting forms or you use something like parinfer, which matches parens based on indentation.

Clojure has special syntax for collections of various types, so it's even easier to parse after you get used to it imo.

For me, the bigger challenge was wrapping my head around functional programming using immutable data structures, since that wasn't just syntax, it required me to 'unlearn' thinking in OO paradigm and adopting a new way of thinking about how the program works. You get used to that too after a while.

Lisp is more diffucult to read for most devs because most devs are used to C/Java -like synthax.

If most devs were used to Lisp, it would be the other way around.

It's a chicken and egg problem, at this point.

The parentheses are large glyphs that distract the eye, and do not stand out (to the untrained eye) as delimiters.

Consider:

  (defun split-line (line)
    (remove-if #'(lambda (word) (string= word ""))
               (split-sequence:split-sequence #\Space line)))

Now imagine if we had some "lower weight" glyph besides the paren.

  .defun split-line .line,
    .remove-if #'.lambda .word, .string= word "",,
               .split-sequence:split-sequence #\Space line,,,

Obviously a contrived example replacing () with ., but you can see how "heavy" the parens and how they can dominate what the eye sees.

With experience, the parens vanish. The parens being large and common take control of the conversation more than they should.

> I have not yet encountered a fully satisfying explanation as to why Lisp is perceived as being less readable.

Difficulty is, by definition, relative to one's skill. You cannot so quickly discount the fact that 99% of programming is taught in Java/C style language syntax. If you've had lifelong exposure to Lisp, you might feel exactly the opposite. The author does a poor job of justifying why these pop-cognitive-psych theories should have more weight than prior exposure.

Personally, as someone with decades of exposure to both styles, I look at the factorial example and see everything I love about Lisp syntax - consistent, no magic keywords and syntax to memorize, it represents a tree just like my mental model of code, there's no way to fall through and forget an else, expressions instead of statements, no early returns ... literally everything about the Lisp example is more readable to me. YMMV.

I love lisp and think it’s amazing. One of the things that commonly throws me off when I haven’t been writing it very much day to day is sometimes it’s unclear what’s going to be returned by a function.

An explicit return 0 is a lot more obvious than just having a 0.

Also, I’ll agree that a ‘ or a , in the wrong place is very easy to visually miss, then you can read a totally different meaning out of the code.

I don't think it's ONLY the parenthesis, it's also the lost opportunity to do meaningful things with indent that bothers me. For example: a missing end paren is often obvious where it should end to a human reader because the next definition starts at some set indent level (0 being the most obvious one). But we talk a different language to the compiler and to the human so the error message is far from where it would be useful.

Significant whitespace is actually a good thing™, even if you only use it to narrow compiler error messages. You can still have your parens but also get way better error messages if you just use the indent!

I think it has to do more with infix vs. prefix notation - infix is more natural and easier to read.

I tend to struggle with other people's indentation rules for code and other programming languages, like nobody liked my article that said you should carry indentation into embedded strings that represent other programming laguages like SQL

   result = sql.execute("""
      SELECT someColumn
      FROM thatTable
      WHERE anotherValue>55
        AND state='pending'
      ORDER BY createdDate
   """)

Ultimately the idea is that indentation should be influenced by semantics, the intention of the code, and not just the syntax. Of course that is against the "one way to indent" philosophy of Go, Biome, and such... But I might accept less than optimal indentation to put an end to tab wars once and for all.

I find indentation of Lisp always seems to fail at communicating in the semantics, much worse than other languages. Things like

   (if condition truePath falsePath)

are scrambled when your eye skips over something. If the Lisp community got over its respect for tradition perhaps they'd develop some kind of syntax highlighting or tooltips or something that would clarify this sort of structure.

About 90% of real language have subject-verb-object or subject-object-verb orders

https://en.wikipedia.org/wiki/Subject%E2%80%93object%E2%80%9...

verb-subject-object and verb-object-subject are more Lisp-like and represent 10% of languages including Standard Arabic, Finnish and Fillipino.

I like extreme parsimony, like I'd love to write stuff like

   format = lambda: `%1-%2`

but I think as complexity goes up depending on the meaningful order of elements breaks down in many ways and you need to give things meaningful names.

Personally, I find that a lot of LISP hackers put way too much logic into a single form or method rather than breaking it into smaller components that can be composed together. And I think that's often why we see frustration with LISP is that you'll have something that is indented really deep when it could be a much smaller function that's leveraging other functions. It's even worse in certain lisps like Clojure, where you'll see a lot of shorthand symbolic stuff, like for anonymous functions, or when you're using core.async, where you look at it and you think, is this brainfuck?

    (defn foo [] 
       (+ 1 2))

    (defn foo []
      (let [x 2]
         (+ 1 x)))

    (defn foo []
       (let! x 2) 
       (+ 1 x))

Hot take: it's the recursive referential grammar, which does not have an analog in human natural language.

Human languages have hard limits on the reference tracking they support, regardless of syntax (marking, positional grammar, etc.). Humans have to reason to unpack LISP (or deeply nested functions or delegation in other languages).

There is so much conjecture in this article -- take the difference between 'lisp formatting' and 'javascript formatting'. I use so-called 'javascript formatting' (a decided and embarrassing misnomer) routinely when I develop Clojure. This article exudes inexperience with Lisp.

(The(.

People say we can ignore them but I find the difficult to ignore.

But this is not the only problem with lisp syntax. I found that reading Ruby or Python is simply, on average, so much more efficient.

I found scheme somewhat readable - see haxima game world, https://sourceforge.net/projects/nazghul/ it contains scheme files - but I would not want to write any game logic in it.

1. it violates normal syntax rules you have been practicing since you were 4 years old.

Lisp will say:

  (+ (- (\* 3 5) 7) (/ radius pi))

but you are taught since 5:

  (3*5 - 7 + radius/pi)

2. Humans are highly adapted to using language, and understanding language constructs such as implicit context rules. Humans reduce token counts and structure in favor of implicit rules and making common patterns shorter. Lisp makes them all explicit, which forces you to cope with way more tokens. Lexical binding was added to Common Lisp almost as an afterthought, and the way LET/LET* force you to add layers of nesting demonstrates that. Every time you assign a variable the 'modern' way, you have to indent another block of code.

A concrete example is introducing local bindings with actions in between. The thought is "calculate this, do something, then continue":

  user = find_user(user_id)
  require_admin(user)
  report = build_report(user)
  write_audit_log(user, report)
  receipt = send_report(report)
  record_delivery(receipt)

In Common Lisp, a direct translation adds a level of nesting for each binding:

  (let ((user (find-user user-id)))
    (require-admin user)
    (let ((report (build-report user)))
      (write-audit-log user report)
      (let ((receipt (send-report report)))
        (record-delivery receipt))))

This is much closer to what is actually happening, and does not require you to understand scoping rules, but it's cumbersome and stupid.

LET* handles consecutive bindings, but here the actions must happen between them. You can use PROGN inside the initializers, or introduce dummy bindings for the actions, but either way you're restructuring a flat sequence to fit the binding syntax.

That's the implicit context I mean: the statement order combined with syntax rules of the language can supply the scope, without requiring a new enclosing expression every time you introduce a local. Lexical scope itself doesn't require this nesting to be explicit in the syntax of the language and it's not helpful for it to be.

3. So many inconsistencies.

Common Lisp uses alternating keys and values for property lists:

  '(:name "Ada" :age 37)

Association lists use a list of pairs:

  '((:name . "Ada") (:age . 37))

And LET uses two-element binding lists:

  (let ((name "Ada")
        (age 37))
    ...)

Lookup conventions differ as well:

  (getf plist key)
  (gethash key table)
  (assoc key alist)

GETF puts the container first; GETHASH and ASSOC put the key first. ASSOC also returns the matching pair, whereas GETF and GETHASH return the value as their primary result.

4. What happens at COMPILE-FILE time is arcane and almost impossible to keep straight.

5. Common Lisp often feels designed primarily to implement Common Lisp, rather than to write useful application code. Its equality predicates are a good example: EQ, EQL, EQUAL, and EQUALP give you four fixed bundles of rules organized around Lisp's own representations.

Want arrays compared by content? EQUALP does that, but also makes string comparisons case-insensitive. Want objects compared by their slots? EQUALP does that for DEFSTRUCT instances, but not ordinary CLOS instances. Want to define what equality means for your class? None of these predicates is a generic function you can extend.

Checking something basic like "when do these two values mean the same thing?", requires a separate operation of your own. None of the equality operators do anything close to what someone might actually want, unless they happen to be implementing CL in which case they are exactly what you want.

    Comparison                                    EQ   EQL  EQUAL  EQUALP

  Lists containing (1 2)                          NIL  NIL  T      T
  List (1 2) versus (1.0 2.0)                     NIL  NIL  NIL    T
  Strings containing "Ada"                        NIL  NIL  T      T
  String "Ada" versus "ADA"                       NIL  NIL  NIL    T
  Same-type DEFSTRUCT instances, identical slots  NIL  NIL  NIL    T
  Same-class CLOS instances, identical slots      NIL  NIL  NIL    NIL

this actually gets at the real problem. Lisps are wordy as hell. like jesus

  (split-sequence:split-sequence #\Space line)

now imagine if that was

  (split-string " " line)

image if the whole function was

  (defun split (line)
    (remove [\(word) (= "" word)] [split-string " " line]))

or even

  (defun split (line)
    (remove "" [split-string " " line]))

*using [] in place of rainbow parens for clarity of sub arguments

  (split-sequence:split-sequence #\Space line)

  (split-string "a b c")

Lisp is why I started using emacs and its parens matching features.

I don't think the parens are the issue.

But when your function ends with ))))))))) -- that is the issue. Too much shit is being shoved into one method. But this is not the fault of lisp, it's the fault of the programmer who is wielding it.

OMG, the "improved" example is so cluttered and far far far less readable -- and even foreign -- to someone like me that has developed using lisp professionally for at least 10 years.

For syntax highlighting try using a different colour for each level of indentation or parenthesis. I use prism-mode in emacs.

Isn't it extremely common for programming languages to put the verb first? They just write it as verb(...stuff...) instead of (verb ...stuff...).

   subject.verb(object)

   add(left,right)

   a = add(b,c)

   Expression<Number> add(Expression<Number> left,Expression<Number> right)

There's so much crap here, I don't even want to waste my time to unpack.

> Lexical binding was added to Common Lisp almost as an afterthought

Common Lisp was lexically scoped from day one. You're arguing about CL using Elisp's history.

And your "cumbersome and stupid" snippet is that, because, well you wrote it that way.

     (local
       (def user (find-user user-id))
       (require-admin user)
       (def report (build-report user))
       (write-audit-log user report)
       (def receipt (send-report report))
       (record-delivery receipt))
       

In modern Lisp dialect like Clojure it would look even more cleaner.

Lisp is the language where you do whatever syntax is suitable for the task, yourself, in an afternoon. In Python you wait for a PEP.