How newLISP Took My Breath (And Syntax) Away

Translations: δΈ­ζ–‡

A few years ago, a little-known language called newLISP completely changed my understanding of what “good” programming languages look like.

Why newLISP?

Before saying another word, I’d like to address the question that some of my LISP-familiar readers may be asking right now: Why newLISP? Why not Clojure, Scheme, or Common LISP?

The answer is that after evaluating these dialects of LISP, I’ve come to the conclusion that newLISP has several important advantages over other LISPs.

Today, unfortunately, whenever someone mentions newLISP on an online forum frequented by adherents of another LISP, an almost clan-like flame war will erupt. An adherent of one particular dialect, usually someone who has never used newLISP, will shout obscenities such as, “newLISP goes back on just about every advancement made by LISPs”, or “dynamic scope is evil!”

The historical context out of which these sentiments are born is mostly unknown to those observing the debate. As signal gives way to noise, the discussion collapses, the melee disperses, and the bystanders go back to sipping their Java and eating their Pythons.

It is fortunate, I think, that my introduction to the language did not sprout out of one of these battles. It was, for the most part, largely unbiased.

Something called LISP

While attending the University of Florida, I had signed up for a course on artificial intelligence. Our professor predictably introduced the class to a programming language called LISP.

Up to that point in time my knowledge of LISP consisted of the usual hearsay and mantra of those unfamiliar with the language:

“People who like it are crazy zealots who think they’re superior to everyone!”
“It’s mainly used for artificial intelligence stuff.”
“No one uses it for practical purposes.”
“It’s mainly used as a research language.”
“It stands for ‘Lots-of-Irritating-Silly-Parenthesis’. Haha!”

You get the idea. I did not have a clue as to what it was, but I was excited to finally be forced into the position of having to find out. My grade depended on it, after all.

What I discovered was that LISP did in fact live up to its reputation of zealot-inducing awesomeness. Simply being exposed to some of the basic concepts and philosophies of LISP had an immediate and positive impact on my abilities as a programmer.

Syntax: Programmer Enemy #1

LISP’s relative lack of syntax was perhaps the greatest insight, for I immediately felt as though a great weight had disappeared. I realized that it was syntax that was at the root of most programming errors. It was syntax that created a subconscious burden that I had simply been unaware of; causing errors, bugs, and making it difficult to simply turn my thoughts into code. Despite having many years of experience with C-based languages, and being intimately familiar with their syntax, I realized that it was nevertheless a totally unnecessary burden that was slowing me, and everyone else, down.

This is one great advantage of Lisp-like languages: They have very few ways of forming compound expressions, and almost no syntactic structure. . . . After a short time we forget about syntactic details of the language (because there are none) and get on with the real issues.

—Abelson and Sussman

It’s not just the size of the syntax that matters, it’s what you can do with it. What requires layers of special syntax in languages like PHP, Python and Ruby, LISP can do with its basic concepts of lists, functions and symbols. It can do everything those languages can do, in a more elegant fashion, and still have enough tricks left up its sleeve to accomplish feats that are simply not possible in other languages.

Common LISP: A Series of Unfortunate Mistakes

Despite all of these exciting discoveries I still had an uneasy feeling.

Common LISP (CL) was a great departure from what I had known previously, but it reeked of antiquity, and worse, its syntax simply wasn’t very well thought out. The “Zen-like” perfection that it seemed to be yearning for was missing. It was a feeling that Mac users are all too familiar with: There were too many buttons, and most of them were unnecessary.

Common LISP Syntax in a Nutshell

Compared to C++, that’s fantastic. Then again, compared to C++, most languages appear favorable. Having had a taste of the liberty offered by the drop in syntax from C/C++/Java to CL, I did not see why all of this syntax was necessary, and indeed, most of it wasn’t.

Every little piece of syntax that’s introduced into a language adds to the programmer’s mental burden, be he conscious of it or not. I was not prepared to spend the effort learning Common LISP if a better alternative could be found.

What do you mean by “syntax”?

You may object at my inclusion of the functions defvar, =, eq, eql, etc. as they are functions. I include them because they constitute low-level functionality that cannot be expressed in the syntax of LISP itself. In other words, the functions = and eq are low-level primitives that must be defined in the language that LISP itself is implemented in, and their meaning and usage cannot be deduced from any other existing LISP syntax.

Consider PHP’s != and !==, they are both operators and are used in the same way, yet that doesn’t tell you anything about what the difference between them is. There’s no way to deduce their meaning from the existing semantics of the language and thus they each represent new syntax that must be learned.

How I Discovered newLISP

The professor revealed to us our “major class project”: we were to implement a text-based version of the game Chainshot:


An implementation of Chainshot

Chainshot starts with a grid completely filled with colored cells. Your goal is to clear the board and you do this by clicking on each cell. If the cell has any adjacent cells of the same color, they all disappear. The effect spreads to include all of the cells adjacent to those, and so on. Cells then drop down to fill in the gap left by the vanished group. If an entire column disappears then all cells to the right of it move left to fill it in. There’s a wonderful and free implementation of this for OS X called Otis.

For the midterm we were to make a version of this playable by a human, and for the final we had to write an AI to play the game.

“One more thing…” he said, “If you do it in LISP, you’ll get a 10% bonus.”

The problem though was most of the lectures focused on various algorithms and theory for doing AI. Those who wanted the 10% bonus would have to teach themselves the language.

Most students chose to forsake the bonus in favor of using a language that they were already familiar with, and like most students I had very little time, so I was partial to that sentiment. However, I decided to do a Google search to see if I could find a Common LISP alternative that was more appetizing.

To my delight I found a language that seemed to check all the right boxes, and surprisingly it wasn’t Scheme (although that is a wonderful language as well). Like Scheme, this language had greatly simplified Common LISP’s syntax, but at the same time it came with a standard library full of useful functions for performing modern scripting tasks, and all you needed to run it was a single tiny executable!

Discovering newLISP

newLISPHere is what ultimately turned me into such a fan of newLISP.

We had several months to complete the first part of the project, and the night before it was due, I did not have a single part of it complete. I had spent the night working on other things, and for perhaps an hour I spent some time looking over the newLISP website, reading about it.

The next day, approximately four hours before I was to hand in my finished, playable version of Chainshot, I sat down at a desk, put on my headphones, and proceeded to simultaneously learn newLISP while creating this game with it.

I finished in about 3 hours, of which only about ten minutes was spent debugging. I was dumbfounded. I had discovered something new, a language that allowed me to rapidly write what, after years of C-based languages, seemed like virtually “bug-free code” that just worked. It was a language that I had come close to mastering in a matter of minutes, having never used it before! In the time I had learned newLISP and written a text-based game in it I would probably only be finishing the tutorials for Ruby or Python.

newLISP’s Strengths

At the beginning of this post I made the claim that newLISP has several advantages over the other LISPs. They can all be summarized as follows: If you want a LISP-based scripting language, choose newLISP.

Before getting into the details let me warn:

newLISP is not a general-purpose programming language.

In the same sense that you wouldn’t use JavaScript to write an iPhone app (some beg to differ), you wouldn’t use use newLISP to write an operating system, a music player like iTunes, or a web browser like Firefox. For such endeavors I recommend without hesitation Clojure, Scheme, C, Objective-C, etc. In other words, languages geared for solving complex, low-level problems, as quickly as possible.

The very first sentence on newLISP’s website states (emphasis mine):

newLISP is a Lisp-like, general-purpose scripting language.

Long ago, when computers were slow, the LISP community was mercilessly mocked by their C and Assembly-wielding counterparts for the crime of being too slow. Ever since that time the subject of performance has been a sore spot for the LISP community from which, I dare say, it has yet to fully recover. Its focus turned towards compilation and proving to the world that it too, could be fast. As a result, few seem to have noticed the need for a general-purpose LISP focused instead on interpretation and scripting.

Luckily, newLISP seems to fit that role rather well. It is a general-purpose interpreted scripting language. It’s my understanding that because of how dynamic it is, it cannot even be compiled to bytecode (this does not mean it is not fast, though).

Without this understanding, some of its design decisions will not make sense. Why choose fexprs over macros? Why dynamic scope instead of lexical scope? Why One-Reference-Only memory management instead of garbage collection?

Design and Syntax

newLISP comes in a single, tiny 200+KB binary executable. Out of all the LISP derivatives I’ve tried, it is the easiest to setup, deploy, and develop for. Somehow that tiny package contains the entire language and includes functions for reading and writing files, parsing text, regular expressions, running code in parallel, over a network, and much more. For the final project I was the only person in the class to submit a fully parallelizable AI (scalable to any number of cores) to solve each grid. The only reason I did it was because I could do it without breaking a sweat. newLISP made it mind-numbingly easy, and this was before it had all the actor and Cilk stuff.

newLISP’s syntax is minimalist and well thought out. For the sake of comparison with the Common LISP syntax card, I’ve kept most of the attributes (such as font size) the same:

newLISP in a nutshell

Functions do not need any of the &rest, &optional flags. Simply pass in variables or don’t, the parameters that don’t get anything are set to nil, and extra stuff can be accessed through the function (args) or the symbol $args.

Functions, like most other things, evaluate to themselves. You don’t need a special #’ syntax to access them. Functions are also real lists. This means you can get their source after they’ve been defined, and even modify them while they are executing.

fexprs and eval

Instead of macros newLISP chose to use fexprs, or functions that simply don’t evaluate their arguments (although to the chagrin of some, newLISP calls them macros). This decision makes sense because in an interpreted LISP, almost everything happens at runtime and there are situations where fexprs can be much faster to execute than macros. It also means that newLISP’s “macros” don’t need the special backquote syntax, making them easier to write and read.

You may have heard the mantra against using eval in other languages. In newLISP, this just doesn’t apply. newLISP’s eval is faster than other LISPs.

This has many consequences, one of which is that sometimes newLISP’s fexprs can be faster than compiled macros in the other LISPs, but also it means that using eval is no longer frowned upon, which opens up all sorts of coding possibilities.

Equality and Memory Management

Notice that there’s a single equality operator, the equals sign. newLISP can get away with this luxury because of its memory-management model, called One-Reference-Only (ORO).

In short, most things are passed by-value and so you end up not needing all of those ridiculous comparison functions. If two things have the same value they are equal—end of story (except in the case of Objective newLISP).

This is not as crazy as it sounds. Internally, newLISP passes data by reference between built-in functions and does other optimizations. You can pass data by reference through the use of contexts and symbols, or by using Objective newLISP. newLISP’s ORO also means repeatable code execution times; you’ll never experience “GC Hell” because there is no garbage collector.

Dynamic Scope

Much fuss is often made over newLISP’s use of dynamic scope. It is true, dynamic scope can be dangerous!

In a similar way, pointers and alcohol can be dangerous too! That doesn’t mean you shouldn’t ever program in C or enjoy yourself at a party. Check for NULL, don’t drink and drive, and beware of “free variables.”

Remember, newLISP is an interpreted language. Lutz Mueller, the author of newLISP, made a simple cost/benefit analysis and chose dynamic scope because it’s faster than lexical scope, and because it’s very easy to avoid the potential pitfalls of dynamic scope. Instead of this:

(define (my-unsafe-func)
    (println my-var)

Do this:

(define (my-safe-func my-var)
    (println my-var)

It’s a small price to pay for the performance improvement, and oftentimes it’s actually quite handy to have dynamic scope (especially in combination with the no-longer taboo eval). If you need lexical scope though, newLISP has you covered.

Parallel Processing

newLISP takes an interesting approach for running code in parallel. Whereas Clojure uses advanced methods for multi-threading and ensuring safety, newLISP simply uses its small size and lets the Operating System do all the work!

There are no threads. Writing safe, parallel code is simple through actors and spawn/sync because newLISP simply forks itself. Its modest stature makes this a fairly cheap operation, allowing the OS to handle scheduling and memory-protection. Try forking a JVM… πŸ˜›

Excellent Documentation and Community

newLISP’s documentation is one of the best examples of excellent documentation that I’ve ever seen, simply surpassing the documentation for any other LISP that I’m aware of. You don’t need to shell out money for a book to learn it, and that’s because it doesn’t need a book! The short manual included with the reference documentation is all you’ll need to learn the language. Its documentation is one of the primary reasons that I was able to successfully procrastinate for my midterm.

If I had to pick a word to describe newLISP’s community it would probably be “cozy” (and for Common LISP it would probably be “abrasive”). Everyone’s question is heard and answered in a friendly and rapid manner, and there is no formality. Lutz Mueller will often answer your question or incorporate your suggestions directly into the language. It’s a small community, yes, but it’s also agile and capable of rapid change without politics.

Other Goodies

There are many other goodies that I won’t dwell on:

Conclusion + Related Links

newLISP is a true diamond in the rough, sorely under-hyped, but a thing of beauty nevertheless.

If you found this post interesting, you may find some of the links below worth visiting:

27 thoughts on “How newLISP Took My Breath (And Syntax) Away

  1. Reply

    Brad Cater

    Any chance you could share your Chainshot code?

  2. Reply


    That’s fascinating. I haven’t wanted to learn lisp because of time constraints. Sounds like there is no excuse with newLisp. Will definitely look into it. Thanks.

  3. Reply


    Fascinating – a good story, and an impressive achievement in 3 hours. I hope you got your 10% bonus!

  4. Reply


    This is a wonderful write up. I had been going back and forth trying to figure out which (Clojure or newLISP) language to learn this year, and this article answered the majority of my questions in what seemed to be an unbiased fashion.

    I will say the one spot that made me wince was the “look how productive it made me” that seems to resonate with most write ups about “new-ish” languages.

    Regardless, I’m looking past that and drinking the kool-aid anyway. Nicely done!

  5. Reply

    Tim Dysngire

    What are the “newLISP has several important advantages over other LISPs” that you don’t list? Don’t get me wrong – I love all lisps – but I program in clojure full time. What’s newLISP got as an advantage except no libraries and little community ?

  6. Reply

    Mark Wotton

    a sane implementation of lexically scoped variables will actually generally be faster than dynamic scoping, as they can be computed as static offsets against the environment rather than requiring a lookup table. the perception of lexical scoping as slow is a historical artifact.

  7. Reply


    In addition to the features you mention, you could have mentioned the “NetEval” feature. That is you can sling s-expr’s around to multiple nodes and with virtually no extra code have cluster and parallel processing.

    In the rare cases that I need to debug something it is possible to telnet to a node performing a specific function and work out what is causing the issue.

    The one gripe: I haven’t found a really easy way to do GUI programming, e.g. like Tkinter in Python ( of course I hate the Tk/TCL overhead).

  8. Reply

    Greg Slepak Post author

    @Brad, the chainshot code is very old and no longer runs on the current version of newLISP. For the final we did have to create a writeup discussing how our method worked, along with a full listing of the source. If you want that I have it available in PDF form, just shoot shoot an email to the address on the “About Us” page and I’ll send it to you. I don’t want to post it publicly because I believe the professor still uses this project for his classes, and I’m afraid it would encourage cheating.

    @Tim, I’m not sure how to answer your question as that is sortof what this entire post was about: newLISP is better suited than Clojure is for scripting, but that does not mean that it is better than Clojure in general. Use both for the tasks they excel at. I’ve never been at a loss for some library (especially since newLISP gives you easy access to every C library), and its community is very helpful.

    @Mark, can you provide something to backup your claim? The fact remains, something is causing newLISP’s eval to beat all the others, and I wouldn’t be surprised if dynamic scope plays a role in that.

    @CyberED, I did mention it, if indirectly. See the link in the “other goodies” for “Simple and powerful distributed computing.” πŸ™‚

  9. Reply

    Mark Wotton
    “variable lookup is always very efficient with static scope, as the location of each value is known at compile time.” goes into a bit of the history as to why dynamic scoping was thought to be more efficient.

  10. Reply

    Greg Slepak Post author

    @Mark, thanks for the link, it’s was a very interesting story but unfortunately the entire thing is about compiler optimizations. The quote from the wiki, you’ll note, is also about compilation. newLISP has no compiler. This was stressed multiple times in the post: newLISP is a Lisp-like, general-purpose interpreted scripting language. The “location of each value” is not known.

    Until you produce something that discusses how lexical scope is faster in an interpreted language, I think I’ll trust in the benchmarks of newLISP’s eval and Lutz Mueller’s expertise. Everything that I’ve read so far seems to indicate that indeed, dynamic scope is the better choice to use for a Lisp geared towards scripting.

  11. Reply

    Mark Wotton

    an interpreter knows strictly more about the code it’s got than a compiler, though. There’s no reason you couldn’t do the same analysis: if you adopted lexical scope, the interpreter would still know the offset into the environment.

    anyway, why argue when we have data:

    17:03 ~/bench % cat ack.lisp
    #!/usr/bin/newlisp -s1000000
    ;; Ackermann’s Function
    ;; By Brent Fulgham
    (define (ack m n)
    (cond ((= m 0) (+ n 1))
    ((= n 0) (ack (- m 1) 1))
    (true (ack (- m 1) (ack m (- n 1))))))

    (define (main)
    (set ‘N (integer (last (main-args))))
    (format “Ack(3,%d): %d” N (ack 3 N))))


    17:04 ~/bench % cat ack.scm

    #lang scheme
    (define (A m n)
    ((= m 0) (+ n 1))
    ((= n 0) (A (- m 1) 1))
    (else (A (- m 1) (A m (- n 1))))))

    (let ((n (string->number (vector-ref (current-command-line-arguments)
    (A 3 n))

    17:04 ~/bench % time mzscheme ack.scm 9
    mzscheme ack.scm 9 0.29s user 0.05s system 93% cpu 0.368 total
    17:04 ~/bench % time ./ack.lisp 9
    Ack(3,9): 4093
    ./ack.lisp 9 6.07s user 0.04s system 98% cpu 6.202 total

    mzscheme is a Scheme interpreter, so uses lexical scoping, and at least on this test is 20 times faster on a function-call heavy benchmark, which should test efficiency of variable lookup. There may be semantic reasons to use dynamic scoping, but performance is just a non-starter.

  12. Reply

    Kazimir Majorinc

    Mark, MZScheme is JIT compiler, isn’t it? Results you published are consistent with results at

    You’ll see that PLT = Mz is very similar to Lispworks, Clozure and Allegro compilers. I.e. much faster than Newlisp if code doesn’t contain eval, and slower if it does. [Newlisp eval is fast because NL is closer to pure interpreter. Compiling is too expensive if some code (without loops) will be evaluated only once.]

    One can test lexical vs dynamic scope in CL, because CL allows both.

    I’ve spent one year using PLT. Excellent IDE, lot of tools, very helpful community.

    Greg, nice article. 3.5 hours is impressive.

  13. Reply


    What you see in this benchmark is probably the speed difference of continuation style passing in recursive functions in a Scheme, not a speed difference between dynamic and lexical scoping.

  14. Reply

    Marc Hildmann

    Thanks buddy for this great post and Your good work on Dragonfly!

  15. Reply

    Nicholas E. May

    Thanks so much for writing this, I’m totally going to give newLISP another look. Kudos for being straightforward, well-written and unbiased.

    Also? Your site design is yummy.

  16. Reply

    Xah Lee

    problem with wanting to learn new lang is that there are so many, all says β€œi’m best”. Although i heard of newLISP, never had energy or need to read about it for more than 20 min.

    but with blogs, it’s like reading tabloids. It’s fun pastime. I saw this title, felt must read it! Then, unawares, it gave me a nice intro to newLISP.

    very nice article. Thanks a lot.

    about the including of γ€Œdefvar」, γ€Œ=」, γ€Œeq」, γ€Œeql」 in the syntax, am not sure i agree with the justification. By your justification, it should also include γ€Œ;」, γ€Œ#| |#」, γ€Œ[]」, γ€Œ1+」, γ€Œ<」 and i think a lot others.

    however, i think it's nice the way you had it, because it does give a sense of the comparitive complexity of Common Lisp vs newLISP's syntax.

    i find it hard to swallow for the justification of dynamic scope though… even suppose due to its faster speed, how many microseconds one might save today?

  17. Pingback: Tweeting frequency « newlisper

  18. Reply


    newlisp cannot calc fac(30) ?!
    >(define (fac n) (if (= n 1) 1 (* n (fac (- n 1)))))
    >(fac 30)

    using ECL
    >(defun fac (n) (if (= n 1) 1 (* n (fac (- n 1)))))
    >(fac 100)

  19. Reply

    Vidyuth Kini

    A Wonderful post, beautiful actually, proselytisation extraordinare.

    I’m a lisp newbie but I’ve played around with CL, scheme, racket, closure, emacs etc… Sicp, little schemer and Land of lisp opened my mind.

    So far, I’ve really liked newLisp. Feels better as a scripting language.

  20. Reply


    The best thing about it is that it starts up almost three times faster than clojure. That made my decision very easy when it came to choosing a language for my command line app. And to top it up, it has a regex library in the standard installation. I had tried without success to use cl-ppcre and asdf in clisp before that. It’s repl leaves much to be desired though- the whole expression has to be in one line!! All in all bye bye cl weenies, its newlisp all the way baby. Domo aregato!!

  21. Reply


    Hi Greg,

    I’m curious if your feelings about newLISP are the same, now that you’ve had a few years to explore and use it more in depth. Has your experience with it continued to be as positive as your initial impression?

    1. Reply

      Greg Slepak Post author

      Hey Nick, thanks for checking in! πŸ™‚

      I still really like it. What has happened over the years is that my understanding of the situations it’s good for has matured.

      newLISP has to flaws that limit its use:

      1. Its ORO memory design, while good in some ways, fundamentally limits its ability to be used for complex programs. My Objective newLISP mitigates that issue somewhat, but no one seems to have used it besides me.

      2. Speaking of which, the second issue with newLISP is that its community is still very small, in spite of my evangelism. This means fewer libraries, and more libraries that are out of date.

      3. There are other scripting languages that are also very simple that have caught my eye, and yet in many ways are better suited for many tasks. For me, CoffeeScript + NodeJS has taken over web-dev type stuff, where it used to be newLISP + Dragonfly that I would use (I still use that btw for our order backend).

      So, the kinds of situations that I use newLISP in these days are the kinds of situations that others might use Shell Script for. Small scripts, data extractions and manipulation, etc. Things that I don’t need a large community for in other words. πŸ˜›

      As great as CoffeeScript is, because it’s not a Lisp, it can never do some of the amazing things that newLISP can do, so I still keep newLISP around. πŸ™‚

      1. Reply

        Greg Slepak Post author

        Oh, I forgot to mention: since writing this post I also introduced myself to Clojure. Clojure and newLISP are surprisingly orthogonal though, they don’t really seem like competitors to me.

        Clojure is really nice for writing beefy servers in that nobody else will understand or maintain, so because of that CoffeeScript + NodeJS has actually replaced Clojure for me.

        1. Nicholas E. May


          Just got a ping in my e-mail from my original comment four years ago — after newlisp I tried many others — including Racket (, a grown-up version of Scheme that is taking the language in new directions. It used to be knows as PLT Scheme. You might find that useful — everything I’ve heard about Clojure is excellent though, and I really enjoyed watching Rich Hicky’s original presentations about the language theory. I just wish it didn’t require the JVM and I might give it a try sometime.


    2. Reply

      Greg Slepak Post author

      How bout yourself? What are your thoughts on the whole thing?

      1. Reply


        Well, I’ve been a Rebol user for more than a decade, so I’m not easily frightened off by small community πŸ˜‰ I think Rebol and newLISP share some of the same goals and ethos, so it’s interesting to hear that you ended up in CoffeeScript + NodeJS land, especially after evangelizing newLISP, and appreciating LISP in general. That’s gives me some motivation to dig a little more deeply into those green pastures πŸ™‚ I’d be curious to hear anything about how/why you ended up there.

        1. Greg Slepak Post author

          Re CoffeeScript: probably related to yet another school project actually (finally graduated last year after leaving school for a bit). I ended up deciding to use it for a group project (figuring most people would be ok with learning JavaScript, but deciding that JavaScript sucked too much for me to use it over CoffeeScript).

          The development experience with it (Node+CS), is rather nice, given all the JS/CS tools out there like Grunt/Bower etc.

          Lots of great library support, and because of its async nature, fast too.

          Edit: Also, am currently using it for DNSChain.

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