[Blackthorn]

> Makes absolutely no sense.

Well, for me, it's just not ergonomic. Unlike something like Python.

I solved this year's Advent of Code in Common Lisp in an attempt to learn it better. I determined in the process that the language was awful by 2021 standards and if you wanted a Lisp that was actually usable, go with Clojure or a decent Scheme.

[vegai_]

I can see how Python is clearly more ergonomic than Common Lisp, but I really don't see any significant differences between CL, Clojure and Schemes. Just ergonomic micro-optimizations.

Clojure's native thread-safe data structures are a significant difference, though.

[Blackthorn]

My biggest issues with Common Lisp were:

* Absolutely nothing is consistent. When you mutate something, is the place it goes the first or last argument? No consistency here. * When you pass a value to a function, is it by value or by reference? Who knows? Rules are non obvious, do not follow the principle of least surprise. * Lisp-2 just makes working with higher order functions obnoxious.

One thing it has going for it though is the loop macro, that's admittedly pretty neat.

[kazinator]

There is no "by reference" in Common Lisp; everything is a value. Some values have reference semantics. This makes no difference unless you're mutating, or making unwarranted assumptions about the eq function.

To understand most code, you can just pretend that all values have reference semantics. If mutation is going on and/or the eq function is being used, you have to prick up your ears and pay attention to that detail.

[Blackthorn]

> Some values have reference semantics. This makes no difference unless you're mutating, or making unwarranted assumptions about the eq function.

That's pretty damn far from "no difference"! Once again, rules are non obvious, do not follow the principle of least surprise.

[kazinator]

If you're mutating any object, it is necessarily a value with reference semantics, period. Objects that do not have reference semantics are immutable.

Some objects that cannot be mutated (like numbers) can have reference or value semantics depending on how they are implemented. For instance, a bignum integer always has reference semantics. Small integers usually have value semantics: they fit into a machine word with no heap part. In that case, all instances of the number 0 or 1, and some range beyond that in both directions, will always be the same object according to eq.

If you're mutating an object (and, thus, something that has reference semantics), the difference that the reference semantics makes is that other parts of your program may hold a reference to that object; your code has not received a copy. If you haven't accounted for that, you probably have a bug.

Sure, this stuff isn't obvious; unless you already know another dynamic language like Ruby, Javascript, Python, ...

Complete neophytes have to be taught it from the fundamentals.

[Blackthorn]

No, there really is no consistency to Common Lisp's mutation.

  $ sbcl
  * (defvar a (list))
  A
  * a
  NIL
  * (defun x (v) (push 'b v) v)
  X
  * (x a)
  (B)
  * a
  NIL

Now if you were to do similar with something like an array, the original variable would be mutated. Just another example of how Common Lisp doesn't have any sort of internal consistency. Once again, rules are non obvious, do not follow the principle of least surprise.