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Comment by mahmud | Hacker News Reader

Good grief.

No.

Lisp-N has to do with the number of name spaces in the language. Lisp-1s only have ONE environment; the variables range over all values of the language, integers, functions, vectors, symbols, strings. In Lisp-N, there are N namespaces for each "kind" of value.

Common Lisp is called a "Lisp-2" because it separates functions from other values. (it's closer to Lisp-5 or even Lisp-7, forgot which, because it allows that many kinds of "names" without collission.

Also above you said Clojure "probably" has better data structures than Common Lisp. That is unsubstantiated.

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For what it's worth, Clojure has implementations of Phil Bagwell's HAMT-based hash-maps, vectors, and sets. These are absolutely amazing data structures, and offer functional updates, a list-like API (O(log_32(n)) for most operations, which ends up being less than seven operations in practice, which is similar enough to O(1) for most programmers).

I'm not much of a common lisp programmer (mostly sticking with scheme/racket and Clojure), but I don't think they've been ported to Common Lisp (yet), so the claim that Clojure has better data structures than Common Lisp, while somewhat a matter of preference, isn't entirely unsubstantiated.

Common Lisp has hash-tables, vectors, and sets .. had it, in an ANSI-specified document since 1984. The implementation details of these is, well, implementation dependent, be they HAMT or whatever.

The language provides a wealth of tools out of the box, but it's the job of the programmer to choose more appropriate tools for the problems at hand.

The following is the Common Lisp specification. 12+ implementations, half of them industrial strength, more than half commercial vendors, and everyone of them has to adhere to this spec:

http://www.franz.com/support/documentation/8.2/ansicl/ansicl...

Note that CL's data structures are mutable, whereas Clojure's are persistent.

Google search saver: immutable = persistent

But does Common Lisp allow multiple implementations of those data structures to exist in the same program actually allowing programmers to utilize the best tool for the job?

Are you seriously asking me if a programming language allows for the implementation of data-structures?

If you mean can users extend the core CL data-types, no, but you have a wealth of tools to do that yourself; use generic functions to implement whatever interface you wish, then provide for specific implementations.

but you have a wealth of tools to do that yourself

That's the problem. With Clojure you don't have to invent interfaces and then convince other libraries to use them. All the data structures are built upon well considered language level protocols that anyone can implement preventing pointless API proliferation.

Clojure has the benefit of hindsight; it is one of the newest programming languages and it is not constrained by a published standard, nor does it need to cater to tens of vendors or any existant code-bases (Nearly every user of Clojure is on github ;-)

I think wise people prefer programming in good languages that enjoy the benefit of hindsight. Common Lisp does not have the luxury of hindsight, and can hardly change its specification to reflect modern theoretical and practical PL results.

Personally, I slightly prefer Clojure over SBCL.

yoklov, for some reason I can't reply directly. There are a few common lisp libraries of persistent, immutable data structures that perform well. This one is implemented most closely to Clojure's: https://github.com/ks/X.FDATATYPES . This one has been around for a long time and is quite stable: http://common-lisp.net/project/fset/Site/index.html .

> Also above you said Clojure "probably" has better data structures than Common Lisp. That is unsubstantiated.

It is my understanding that Common Lisp lacks the vector and hash maps that Clojure has.

Sorry if I got it wrong. I am more a ML guy than Lisp.

Your understanding continues to be wrong.

http://www.lispworks.com/documentation/HyperSpec/Body/t_vect... http://www.lispworks.com/documentation/HyperSpec/Body/t_hash...

I was wrong it seems.

From the documentation I have not seen the simplified syntax Clojure uses for vectors, hashes and sets.

I imagine that the syntax is Clojure specific.

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