I know that the purpose of the page is to compare syntax of common lisp, racket, clojure, and emacs lisp.
But some examples could be more idiomatic, for instance instead of
(defun add (a &rest b)
(if (null b)
a
(+ a (eval (cons '+ b)))))
One should avoid eval and use endp instead of null:
(defun add (a &rest b)
(if (endp b) a
(apply #'add (+ a (first b)) (rest b))))
The use of cl:eval alone is enough to make me believe that the CL column was never reviewed by an experienced CL programmer. I am now more suspicious of the other columns, which are languages I'm far less familiar with.
Almost. It should be (+ a (apply #'+ b)). Common Lisp is a Lisp-2, so a + in the argument position is assumed to be a variable named +, not the function named +, unless you specify otherwise.
All major Common Lisps support tail call optimization with proper declarations, with the exception of ABCL because it runs on the JVM.
And those declarations are all identical or almost identical, so it's easy to write an implementation-specific macro to guarantee TCO if you need to do so.
Some algorithms are easiest to express and read with looping constructs. For those algorithms, use looping constructs. Other algorithms are easiest to express and read with recursion. For those, use recursion. You shouldn't be afraid of recursion just because ANSI doesn't say TCO is guaranteed. You should be afraid of it if your code needs to run on ABCL, but otherwise, recur on.
I think it is fair to say that the CL community is divided on whether or not relying on TCO is idiomatic.
I prefer to write my state-machines as transitioning with tail-calls, and I do get called for it. It's relatively easy to switch something written in that manner to using a loop with a trampoline, so I do so when my collaborators request it.
I wouldn't argue about things that are a matter of taste normally, except that I've had the experience where I've turned down optimizer settings in order to debug some code better and then the had stack overflow.
Sigh and yet it continues to be true. You can make a pragmatic decision and rely on tail call optimisation for your specific case, but if you are writing a CL library, then it is not idiomatic to use recursion in the same way that you would for Clojure or Scheme.
Even with SBCL, for example, it doesn't have tail-call optimisation for all architectures at all optimisation levels.
- why nothing on the "compiler" line? Everytime you load a snippet or a file with SBCL, it compiles it (to machine code). There's also compile-file.
- interpreter: likewise, all code is compiled by default with SBCL, not interpreted, even in the REPL. To use the interpreter, we must do this: https://github.com/lisp-tips/lisp-tips/issues/52
- command line program: the racket cell shows the use of -e (eval), the same can be done with any CL implementation.
- since the string split line introduces cl-ppcre, one could mention cl-str :D (plug) (much terser join, trim, concat etc)
- ah ok, for dates and times, flattening a list, hash-table literals… we need more libraries.
Since you are also commenting libraries, I think that FSet (1) for inmutable memory,and perhaps a comparison with clojure, and the quick-lisp package manager could be mentioned.
The page indicates that there is not function for documentation in common lisp, but
(documentation 'documentation 'function)
"Return the documentation string of Doc-Type for X, or NIL if none
exists.
System doc-types are VARIABLE, FUNCTION, STRUCTURE, TYPE, SETF, and T.
Also http://rosettacode.org for computer tasks implemented in many computer languages to allow you compare syntax and code.
To be fair I think the only real differences since 1.6 you’d see are transducer versions of some of what’s in here for Clojure. The stuff expressed here is all very basic.
Emacs Lisp is a descendant of PDP-10 MAClisp, which makes it one of the oldest Lisp dialects still actively maintained. Whether it's version 24.5 or 30.2 doesn't make much of a difference semantically.
Something I've been meaning to do is try putting together a cross-lisp package manager -- if only because it'd be fun. Maybe it would favor code that could be readily run or eval'd or maybe with some sort of clj/cljs type dynamic dispatch for anything implementation specific.
As someone who's not a programmer but has beginner - medium python & C skills. I'm in middle of learning lisp (elisp to be precise) and it feels like reading poetry. It's a transcendent experience that's hard to explain. Such beautiful concepts. Everything flows in a way it doesn't in C based langs
But makes me think we'd be better off if we all just focused on a single one, and grew it, made it better. Not having 4 versions of something almost identical. Fragmentation can hurt adoption.
Personally I prefer lisp 1 languages, like scheme. Even there, though, there was a split over r6rs, so we got a bunch of mostly-like-r5rs schemes and racket.
Maybe the problem is that lisps are no longer popular enough to have a winning implementation! If there is one, though, then it's Common Lisp on SBCL.
CL list comprehension:
I know that the purpose of the page is to compare syntax of common lisp, racket, clojure, and emacs lisp. But some examples could be more idiomatic, for instance instead of
One should avoid eval and use endp instead of null:The use of cl:eval alone is enough to make me believe that the CL column was never reviewed by an experienced CL programmer. I am now more suspicious of the other columns, which are languages I'm far less familiar with.
Shouldn't it be (+ a (apply + b))
Almost. It should be (+ a (apply #'+ b)). Common Lisp is a Lisp-2, so a + in the argument position is assumed to be a variable named +, not the function named +, unless you specify otherwise.
Worse: Using recursion in Common Lisp isn't idiomatic, given that CL doesn't guarantee tail-call optimisation in the specification.
Sigh. This again.
All major Common Lisps support tail call optimization with proper declarations, with the exception of ABCL because it runs on the JVM.
And those declarations are all identical or almost identical, so it's easy to write an implementation-specific macro to guarantee TCO if you need to do so.
Some algorithms are easiest to express and read with looping constructs. For those algorithms, use looping constructs. Other algorithms are easiest to express and read with recursion. For those, use recursion. You shouldn't be afraid of recursion just because ANSI doesn't say TCO is guaranteed. You should be afraid of it if your code needs to run on ABCL, but otherwise, recur on.
I think it is fair to say that the CL community is divided on whether or not relying on TCO is idiomatic.
I prefer to write my state-machines as transitioning with tail-calls, and I do get called for it. It's relatively easy to switch something written in that manner to using a loop with a trampoline, so I do so when my collaborators request it.
I wouldn't argue about things that are a matter of taste normally, except that I've had the experience where I've turned down optimizer settings in order to debug some code better and then the had stack overflow.
Sigh and yet it continues to be true. You can make a pragmatic decision and rely on tail call optimisation for your specific case, but if you are writing a CL library, then it is not idiomatic to use recursion in the same way that you would for Clojure or Scheme.
Even with SBCL, for example, it doesn't have tail-call optimisation for all architectures at all optimisation levels.
Notes on CL:
- why nothing on the "compiler" line? Everytime you load a snippet or a file with SBCL, it compiles it (to machine code). There's also compile-file.
- interpreter: likewise, all code is compiled by default with SBCL, not interpreted, even in the REPL. To use the interpreter, we must do this: https://github.com/lisp-tips/lisp-tips/issues/52
- command line program: the racket cell shows the use of -e (eval), the same can be done with any CL implementation.
- since the string split line introduces cl-ppcre, one could mention cl-str :D (plug) (much terser join, trim, concat etc)
- ah ok, for dates and times, flattening a list, hash-table literals… we need more libraries.
- more files operations: https://lispcookbook.github.io/cl-cookbook/files.html
- emacs buffers: now compare with Lem buffers 8-)
- posix-getenv: I'd rather use uiop:getenv (comes in implementations).
- uiop:*command-line-arguments*
- exit: uiop:quit
- uiop:run-program (sync) / launch-program (async)
- java interop: with LispWorks or ABCL (or other libraries)
my 2c
> - ah ok, for dates and times
local-time has its limits (e.g. Gregorian only), but it does everything listed in this chart
> flattening a list
What? Isn't this[1] just fine (<s>)
> hash-table literals…
Since the chart is sbcl specific, this ugly mess would technically count; a more portable (but longer) version could be made similarly using #.:
> java interop: with LispWorks or ABCL (or other libraries)I've had good luck with .net/java interop using FOIL (written by Rich Hickey prior to Clojure).
1:
=> (A B C D E F)Since you are also commenting libraries, I think that FSet (1) for inmutable memory,and perhaps a comparison with clojure, and the quick-lisp package manager could be mentioned.
(1) https://news.ycombinator.com/item?id=47779659
The page indicates that there is not function for documentation in common lisp, but
Likewise apropos. It's an ANSI function.
Perhaps related, I'm maintaining a "cheatsheet" to let Python programmers see what an Elisp equivalent to typical Python functions/methods are.
https://kickingvegas.github.io/elisp-for-python/
Are `(push s x)` and `(push x s)` correct for push and insert, resp.?
Clojure 1.6, Emacs 24.5... These are pretty old versions, at least of those.
To be fair I think the only real differences since 1.6 you’d see are transducer versions of some of what’s in here for Clojure. The stuff expressed here is all very basic.
Emacs Lisp is a descendant of PDP-10 MAClisp, which makes it one of the oldest Lisp dialects still actively maintained. Whether it's version 24.5 or 30.2 doesn't make much of a difference semantically.
Most of the things in that table won’t change from version to version anyway.
This is really neat.
Something I've been meaning to do is try putting together a cross-lisp package manager -- if only because it'd be fun. Maybe it would favor code that could be readily run or eval'd or maybe with some sort of clj/cljs type dynamic dispatch for anything implementation specific.
Great chrestomathy! I opened a PR for my lisp, Loon: https://github.com/clarkgrubb/hyperpolyglot/pull/139
With all due respect, if this page adds a column for everyone's personal Lisp, it'll be as wide as the Pacific.
They say ethics and aesthetics are one!
Would be interesting to see how Jank is coming along in this space as well.
Jank's just supposed to be Clojure with full compatibility, when mature.
As someone who's not a programmer but has beginner - medium python & C skills. I'm in middle of learning lisp (elisp to be precise) and it feels like reading poetry. It's a transcendent experience that's hard to explain. Such beautiful concepts. Everything flows in a way it doesn't in C based langs
Emacs has cl-lib
https://www.gnu.org/software/emacs/manual/html_mono/cl.html
Nice comparison.
But makes me think we'd be better off if we all just focused on a single one, and grew it, made it better. Not having 4 versions of something almost identical. Fragmentation can hurt adoption.
That’s what Common Lisp is.
You got downvoted, but you're correct. Obligatory XKCD: <https://xkcd.com/927/>
Personally I prefer lisp 1 languages, like scheme. Even there, though, there was a split over r6rs, so we got a bunch of mostly-like-r5rs schemes and racket.
Maybe the problem is that lisps are no longer popular enough to have a winning implementation! If there is one, though, then it's Common Lisp on SBCL.
They are as different from one another as Java is from C# is from JavaScript.
There are deep reasons for the variations, especially around (reader) macros.