pesto5: A concatenative programming library in 5 lines of Clojure
Concatenative styles are making the rounds lately including some interesting examples in Clojure and Haskell. Now I’m perpetually drawn to concatenative languages and their ideas, so I wanted to know what it would take to provide a minimally representative concatenative experience in Clojure.1 As it turns out… not much:
(defn postfix [& e]
(reduce #(if (fn? %2)
(let [[l r & m] %]
(cons (%2 r l) m))
(cons %2 %)) [] e))
This is how it’s used:
(postfix 5 1 2 + 4 * + 3 -)
;;=> [14]
The way that it works is that it treats every non-function as a value and every function as a binary function taking two elements off of a “stack”. It then wraps the answers back up onto the “top” of the stack. The final answer is the stack itself.
This is in no way indicative of a fully blown representation of concatenative programming languages,2 but it was fun and it highlights the stark simplicity of the model. This is my year to finally take concatenative languages seriously. I plan to study hard. I hope you’ll join me.
:F
if you want to talk concatenative languages or pesto5, then feel free to comment below or email me at the address at the top of my blog
-
pesto5 is too small to be a “library”, but a gist will do. ↩
-
It’s debatable if this is concatenative at all, but alas the name pesto5 was too alluring to pass on. ↩
7 Comments, Comment or Ping
Grant Rettke
Not sure any discriminating hacker could participate until you at least mention Forth :P lol.
Jan 6th, 2013
sparist
Great, simple example. Nice to see people interested in concatenative languages.
If you’re interested in a different take on concatenative programming, check out Om. It’s a brand new, experimental concatenative language that uses prefix notation: instead of a data stack, each function takes the remainder of the program for rewriting.
At concatenative.org: http://concatenative.org/wiki/view/Om Website: http://om-language.org
Jan 6th, 2013
geek42
try forth familly languages
Jan 7th, 2013
Dominikus
You might have a look at Consize, a concatenative language I implemented in Clojure in 140 LOC. Consize is very much inspired by Factor, however Consize is a functional language like Joy or Cat is.
http://code.google.com/p/consize/
It is extensively documented in German — I plan to add some documentation in English as well. But you as an Clojure Expert might enjoy reading the source code anyhow ;-) After reading consize.clj, I recommend to continue with prelude-plain.txt.
BTW: Adding object-orientation (i.e. polymorphism via generic words & multiple inheritance much like Clojure does) is possible in about 30 LOC.
Dominikus
Jan 8th, 2013
Ivan Pierre
I prefer to speak of stack programming :). But it was one of my first prefered paradigm before functionnal programming.
There was a goog article by Jon Purdy : http://evincarofautumn.blogspot.ch/2012/02/why-concatenative-programming-matters.html.
and Brandon Bloom the author of the recent fipp wrote a clojure modure based on Factor, a quite interesting approach. https://github.com/brandonbloom/factjor
I thought about stack languages as cuda interface.
Jan 21st, 2013
Brian Beckman
David Liebs and I threw together a concatenative mini-language in Mathematica that does mixed symbolic and numeric computation. The entire thing is implemented, with tooling, in just a few conditional rewrite rules. That’s what is really lovely about concatenative techniques: you get a LOT of expressive power in a very SMALL amount of code, i.e., signal-to-noise ratio is huge!
Feb 12th, 2013
wordpress blog designers
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Feb 22nd, 2013
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