An early Clojure implementation in Common Lisp

http://github.com/clojure/clojure/blob/da14d89c1936e9de6eacb9c12dd9e6a0d68a0829/src/lisp/clojure.lisp

by fogus • 16 years ago

56 29 16 years ago

jjames• 16 years ago

I read the "early" as pre-release and thought someone was trying to re-implement clojure in CL. I'm relieved.

What's the backstory on this, fogus? I've not read about a CL Clojure pre-dating the JVM implementation. Was this just a prototype or was there a plan to platform on CL at some point?

fogus5• 16 years ago

I believe (caveat emptor) that this was an early prototype.

francoisdevlin2• 16 years ago

Does anyone else feel like they're looking at baby pictures?

zachbeane• 16 years ago

http://www.informatimago.com/develop/lisp/small-cl-pgms/aim-...

alexk7• 16 years ago

Now that's "early"! (The link above points to McCarthy texts from 1959 about Lisp)

fogus5• 16 years ago

I wonder what happened to Part 2?

KC8ZKF• 16 years ago

He had DotLisp, a Lisp on the CLR, before Clojure as well.

http://dotlisp.sourceforge.net/dotlisp.htm

http://groups.google.com/group/comp.lang.lisp/msg/e31b38c8cc...

jimbokun3• 16 years ago

I was looking for reader macros for recognizing {} as hash tables and [] as vectors. To me, that is one of the biggest innovations in Clojure over Lisps that came before, the expansion of the concept of S-expressions.

francoisdevlin2• 16 years ago

Personally, my money is on the seq abstraction. YMMV.

jimbokun3• 16 years ago

That is also an excellent choice. But I believe they are related, or at least complement each other, in the sense that all of the data structure literals implement seq. I do not think they would work as well as an extension for S-expressions, otherwise.

Xurinos4• 16 years ago

I am not a CL expert, but I was able to whip this up in short time (and I sacrificed a little readability for brevity):

    (defun set-hash-values (hash pairs)
      (when pairs
        (setf (gethash (car pairs) hash) (cadr pairs))
        (set-hash-values hash (cddr pairs))))

    (defun in-place-hash (stream char)
      (declare (ignore char))
        `(let ((hash (make-hash-table)))
           (set-hash-values hash ',(read-delimited-list #\} stream t))
           hash))

    (set-macro-character #\{ #'in-place-hash)
    (set-syntax-from-char #\} #\))

But to be honest, I think this {} stuff is an abuse of the hash structure. People are really looking to make quick anonymous classes/structs; you see this all the time in the perl world, and now we get to see this abuse promoted and propagated in Clojure. In that case, {} should really translate to a MOP-generated anonymous class.

Also, you are stuck with the decision some developer made for your hash's efficiency trade-offs. In my reader macro, I left things at make-hash-table defaults, but that might not be appropriate for your situation. Do you want to be able to read quickly from your hash in exchange for slow writes, or do you want to be able to write quickly to the hash in exchange for slow reads?

On another note, the [] vector reader macro is much easier to create. I just wanted to prove to myself that I could write {}. But this additional syntax is annoying. In practice when programming Lisp, it is easy to slap in a bunch of ))))) until the right alternate parentheses highlights. Now I have to remember to slap in ] and } at the right spots, leaving me with )]}]]}})) noise. Maybe that is why CL's in-place vector syntax is #().

Anyway, I would hesitate to call {} and [] an innovation.

swannodette• 16 years ago

> Also, you are stuck with the decision some developer made for your hash's efficiency trade-offs.

PersistentHashMaps are not slow. If you think they are, you can provide a custom defrecord with the same fields to the functions of the API and get the all perf benefits without breakage.

> leaving me with )]}]]}})) noise

Guess you never heard of paredit.

> Anyway, I would hesitate to call {} and [] an innovation.

Whatever floats your boat man.

fogus5• 16 years ago

"People are really looking to make quick anonymous classes/structs"

What wrong with that? If you have the need for an anonymous map, then you use a map. If you have the need for a named map then you use a record. Clojure gives you both options.

"Also, you are stuck with the decision some developer made for your hash's efficiency trade-offs."

In that case you just use a different type of hash map. In Clojure you have the choice of the literal syntax (which by the way manages efficiency concerns on your behalf), the hash-map, array-map, or sorted-map functions, or records, or Java maps for interop, or you can implement your own if none of those options work.

nickik2• 16 years ago

1.[], {}, #{} are not the innovation. 2. The innovation is that they are on the same level as lists. All the cool list stuff you can do with lists you can do with all of the structures and you can add more yourself if you want. That allows to write stuff really generic. 3. If you don't like them use (vec ), (map ) and so on. Only the most imported ones have syntax there are many data structures.

P.S. Do you really finish up all your parans yourself???

jimbokun3• 16 years ago

"Anyway, I would hesitate to call {} and [] an innovation."

What made it an "innovation" was the decision to close off access to reader macros from the general public. It sounds like a nice idea to allow people to define the behavior of {}, [], etc. however they like. But the effect is splintering the language even further with fewer reusable idioms.

The Clojure idiom of always using [] for any place you have let-like destructuring makes it easier to quickly visually parse code, for example. The abbreviation for anonymous functions wouldn't be part of the core language if the corresponding reader macro was not claimed by Benevolent Dictator Hickey.

This decision may or may appeal to you, personally, but I think it is one of the things that has quickly allowed Clojure to quickly gain popularity relative to other Lisps.

cemerick• 16 years ago

Note that, unless I'm mistaken, this is from when Clojure emitted Java and C# source. Check out the * host* variable. AFAIK, CL never "hosted" a Clojure runtime.

parenthesis• 16 years ago

Yes, grepping for '(format t ' would seem to confirm this.

bokchoi• 16 years ago

I came across JFLI a Common-Lisp foreign-language interface to Java and was surprised to find it was authored by Mr. Hickey. I wonder how his experience with JFLI shaped Clojure.

http://jfli.sourceforge.net/

nickik2• 16 years ago

To experiment with the language Rich had Clojure Compiler in CL targeting C# and Java.

Then he took time off work and wrote the Java bootstrap compiler.

An early Clojure implementation in Common Lisp

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