Having recently come across this introduction to Factor, I've been a bit curious to learn more. Aside from the official FAQ mentioned there, do you have resources for learning the language (as well as the stack-based "paradigm," if that's the right word) that you've found helpful?
As a side note, would learning Forth help, or is that like comparing C to Python (or what have you)?
You can start here: http://concatenative.org/wiki/view/Factor
And there's a nice documentation included in the runtime/GUI. Just install and then "Browser" and you see the documentation with topics like "Your first program".
The documentation is available online, too: http://docs.factorcode.org/
(It's the same as the one you get when you install Factor.)
Don't forget to subscribe to planet-factor.
I've been teaching myself Factor recently - I actually found Forth as a good afternoon's introduction to the concept of stack based languages (and as a bit of a software archaeologist, it's fun to step back a few years for a history lesson).
To that end I don't think it does any harm to take a few hours to install gforth or similar Forth implementation and start working through the first few chapters of starting forth or using ANS forth - I found it quite interesting, and because I only dipped my toe it hasn't taught me anything I've had to unlearn as I'm starting to learn factor.
Once I've progressed a little further in learning Factor I'll let you know what I've found useful (or not so useful!).
Factor is heavily inspired by Forth and other stack languages. It also grabs ideas from Lisp, and Smalltalk. From what I've read online, it's not necessary to learn any of those language before learning Factor. It won't hurt if you do, however :)
The biggest problems I've run into is the youthfulness of the language. In other words, code samples on various blogs/sites will be outdated because they used older versions of Factor (0.6, 0.7, 0.8, etc). Factor 0.9 and above are most likely to remain the same.
Once you get past the basics, the docs (online + in the listener) are pretty clear. The docs occasionally suffer from the same problem as blog posts: some outdated code examples. You still have the mailing lists/IRC to help out if you really get stuck.
I've only used the docs so far, instead of the mailing lists/IRC. I then experiment with the listener to further learn/explore a new concept I find in the docs.
This is the first language where most of my questions are answered just by digging into the docs of a function. Most of Factor is written in Factor, so things become clearer as you spend more time with the docs.
(The 2nd biggest problem I've had is trying to understand the web framework (Furnace). The web framework is more feature-rich that what I am used to. It's nothing impossible, just requires some practice and exploring the docs.)
The quickest intro. to concatenative languages I've found: http://github.com/raganwald/homoiconic/blob/master/2008-11-16/joy.md#readme
Your first steps to Factor: http://concatenative.org/wiki/view/Factor/Learning
These videos go into more detail regarding writing Factor code:
Some diversions:
Here are some blog posts that can help provide direction:
Understanding the various abstractions and libraries which are available is key to grasping Factor: collections, generic words, fry, locals, macros, memoization, PEGs, the prettyprinter, and so on. Making effective use of these tools can reduce the amount of work required to solve a problem by an order of magnitude.
Factor is definitely the most fun language. It has fewer surprises than other languages. I find it easier to learn than Ruby or Lisp. Just for fun, here is a language shootout between Lisp and Factor:
For anyone who is interested in stack-based languages, this article might help: The Joy of Catenative Languages (Parts 1, 2, 3) (It's more general and uses the Cat language for examples. It helped me with learning Factor basics.)
I think Slava Pestov's excellent presentation "Factor: an extensible interactive language" at Google (Google Tech Talk) counts as a good resource for learning Factor. There are lots of demos of the different aspects of Factor that you should be able to try on your system. For instance the demo of using Factor for implementing an Internet time server, approx. 1 h 07 min 20 secs and lexical closures, 46 min 35 secs. In fact most of the presentation is a demo.
The Flash video is 141 MB, 1 h 36 min 38 secs, presentation time autumn 2008. Slava Pestov is the creator of the Factor programming language and jEdit, a popular text editor.
I hope my interactive tool helps http://factor.openeducationtools.com