# Lambda calculus & functional programming - the view from Ruby **URL:** \ **Category:** Ruby\ **Created:** [June 28, 2008, 11:40pm UTC](https://www.ruby-forum.com/t/lambda-calculus-functional-programming-the-view-from-ruby/141670 "2008-06-28T23:40:33Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![unebaguettesvp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/47e85d/32.png) [@unebaguettesvp](https://www.ruby-forum.com/u/unebaguettesvp)\ **Post date:** [June 28, 2008, 11:40pm UTC](https://www.ruby-forum.com/t/lambda-calculus-functional-programming-the-view-from-ruby/141670/1 "2008-06-28T23:40:33Z")
People, I have a general understanding of lambda calculus & functional programming but I want to know how Ruby fits into this paradigm - is there a summary doc somewhere (preferably with concrete examples) - I couldn’t find anything. What are the advantages/disadvantages, strengths/weaknesses etc of the approach? I am gradually getting a feel for “the Ruby way” and I thought this might help the process. Thanks, ## Phil. Philip R. Pricom Pty Limited (ACN 003 252 275 ABN 91 003 252 275) GPO Box 3411 Sydney NSW 2001 Australia E-mail: removed\_email\_address@domain.invalid ---
**Author:** ![unebaguettesvp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/47e85d/32.png) [@unebaguettesvp](https://www.ruby-forum.com/u/unebaguettesvp)\ **Post date:** [June 29, 2008, 1:37am UTC](https://www.ruby-forum.com/t/lambda-calculus-functional-programming-the-view-from-ruby/141670/2 "2008-06-29T01:37:32Z")
Philip R. wrote: > People, > > I have a general understanding of lambda calculus & functional > programming but I want to know how Ruby fits into this paradigm - is > there a summary doc somewhere (preferably with concrete examples) - I > couldn’t find anything. What are the advantages/disadvantages, > strengths/weaknesses etc of the approach? I am gradually getting a feel > for “the Ruby way” and I thought this might help the process. Well, right off the bat, Ruby allows for global state and side effects (i.e. variables really do vary, and even constants may not be so constant), so while you _could_ (I think) do strict functional programming in Ruby, you would have to be pretty deliberate about it. And since Ruby is ostensibly a message-passing OOP, you might be fighting the language quite a bit. On the down side, even with all that no-side-effect effort, you still won’t get the benefits of a type system as found in, say, Haskell. A strict functional style still may reduce bugs and make the code easier to reason about though. – James B. [www.happycamperstudios.com](http://www.happycamperstudios.com) - Wicked Cool Coding [www.jamesbritt.com](http://www.jamesbritt.com) - Playing with Better Toys [www.ruby-doc.org](http://www.ruby-doc.org) - Ruby Help & Documentation [www.rubystuff.com](http://www.rubystuff.com) - The Ruby Store for Ruby Stuff ---
**Author:** ![unebaguettesvp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/47e85d/32.png) [@unebaguettesvp](https://www.ruby-forum.com/u/unebaguettesvp)\ **Post date:** [June 29, 2008, 3:17am UTC](https://www.ruby-forum.com/t/lambda-calculus-functional-programming-the-view-from-ruby/141670/3 "2008-06-29T03:17:29Z")
Philip R. wrote: > I have a general understanding of lambda calculus & functional > programming but I want to know how Ruby fits into this paradigm - is > there a summary doc somewhere (preferably with concrete examples) - I > couldn’t find anything. What are the advantages/disadvantages, > strengths/weaknesses etc of the approach? I am gradually getting a > feel for “the Ruby way” and I thought this might help the process. > I gave a presentation on this recently. Because Ruby is an object > oriented language, it clashes philosophically with many things that > functional programming holds dear. However, if one can live within these > limitations, then there are ways to make effective use of the functional > style in Ruby, such as chaining methods as if they were functions, which > the Facets library (gem install facets) really helps with. The key lesson is that you want to go with what’s most readable and easiest to maintain for you and your co-workers. In my examples, I progressively went further over the edge into less natural Ruby code, till the final examples looked so weird that you’d never realistically want to write code like that, although it’s nice to know that we have the option. So some of this is useful, and some isn’t. 🙂 Code from my presentation: - [http://www.pastie.org/224206](http://www.pastie.org/224206) – Functional one-liners with their imperative equivalents. - [http://www.pastie.org/224228](http://www.pastie.org/224228) – Reimplementation of something like UNIX “du” in three different styles, with the FunctionalInPlace being generally agreed to as being too weird. -igal ---
**Author:** ![unebaguettesvp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/47e85d/32.png) [@unebaguettesvp](https://www.ruby-forum.com/u/unebaguettesvp)\ **Post date:** [June 29, 2008, 7:26am UTC](https://www.ruby-forum.com/t/lambda-calculus-functional-programming-the-view-from-ruby/141670/4 "2008-06-29T07:26:31Z")
M. Edward (Ed) Borasky wrote: > James B. wrote: > > > A strict functional style still may reduce bugs and make the code > > easier to reason about though. > > I don’t think that’s ever been tested, mostly because every time someone > makes a serious proposal in favor of “strict functional” programming, > the naysayers jump on it and stomp it to death. Not sure what you mean by that, given the existence, and flourishing, of Haskell. However, my best argument would end up being anecdotal, and largely defendant on assertions by, for lack of a better term, the “LtU Crowd”. > Case in point: Read John Backus’ Turing lecture on functional languages, > and contrast attempting to read his code with reading the Rails code. I > think you’ll find it’s easier to reason about the Rails code than it is > to reason about the examples in the Backus paper, or a long string of > combinators in the SKK calculus, or maybe even Scheme code. I don’t see that ad hoc empirical comparisons are going to make a case either way. Again, I don’t have a formal proof of my claim; it’s more of an evolving intuition about code, state, and side effects. I’d be happier looking at Ruby code that minimized passing around state and used isolated metaprogramming. > It all boils down to this: if somebody will pay me to write in a > functional language, I’ll do it. But I’m not holding my breath, nor am I > seeing great numbers of “Help Wanted” ads looking for Haskell, OCaml or > Erlang programmers. I recall when people used that same argument for knocking Ruby. No job listings, so how [good|important|useful] could it be? 🙂 – James B. [www.happycamperstudios.com](http://www.happycamperstudios.com) - Wicked Cool Coding [www.jamesbritt.com](http://www.jamesbritt.com) - Playing with Better Toys [www.ruby-doc.org](http://www.ruby-doc.org) - Ruby Help & Documentation [www.rubystuff.com](http://www.rubystuff.com) - The Ruby Store for Ruby Stuff ---
**Author:** ![unebaguettesvp](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/47e85d/32.png) [@unebaguettesvp](https://www.ruby-forum.com/u/unebaguettesvp)\ **Post date:** [June 29, 2008, 3:53am UTC](https://www.ruby-forum.com/t/lambda-calculus-functional-programming-the-view-from-ruby/141670/5 "2008-06-29T03:53:10Z")
James B. wrote: > A strict functional style still may reduce bugs and make the code easier > to reason about though. I don’t think that’s ever been tested, mostly because every time someone makes a serious proposal in favor of “strict functional” programming, the naysayers jump on it and stomp it to death. Case in point: Read John Backus’ Turing lecture on functional languages, and contrast attempting to read his code with reading the Rails code. I think you’ll find it’s easier to reason about the Rails code than it is to reason about the examples in the Backus paper, or a long string of combinators in the SKK calculus, or maybe even Scheme code. It all boils down to this: if somebody will pay me to write in a functional language, I’ll do it. But I’m not holding my breath, nor am I seeing great numbers of “Help Wanted” ads looking for Haskell, OCaml or Erlang programmers.