[Haskell-cafe] Why functional programming matters

[Derek Elkins]

On Wed, 2008-01-23 at 13:29 +0000, Simon Peyton-Jones wrote:
> Friends
> 
> Over the next few months I'm giving two or three talks to groups of
> *non* functional programmers about why functional programming is
> interesting and important.  If you like, it's the same general goal as
> John Hughes's famous paper "Why functional programming matters".
> 
> Audience: some are technical managers, some are professional
> programmers; but my base assumption is that none already know anything
> much about functional programming.
> 
> Now, I can easily rant on about the glories of functional programming,
> but I'm a biased witness -- I've been doing this stuff too long.  So
> this message is ask your help, especially if you are someone who has a
> somewhat-recent recollection of realising "wow, this fp stuff is so
> cool/useful/powerful/etc".
> 
> I'm going to say some general things, of course, about purity and
> effects, modularity, types, testing, reasoning, parallelism and so on.
> But I hate general waffle, so I want to give concrete evidence, and
> that is what I particularly want your help with.  I'm thinking of two
> sorts of "evidence":
> 
> 
> 1. Small examples of actual code. The goal here is (a) to convey a
> visceral idea of what functional programming *is*, rather than just
> assume the audience knows (they don't), and (b) to convey an idea of
> why it might be good.  One of my favourite examples is quicksort, for
> reasons explained here:
> http://haskell.org/haskellwiki/Introduction#What.27s_good_about_functional_programming.3F
> 
> But I'm sure that you each have a personal favourite or two. Would you
> like to send them to me, along with a paragraph or two about why you
> found it compelling?  For this purpose, a dozen lines of code or so is
> probably a maximum.
> 
> 
> 2. War stories from real life.  eg "In company X in 2004 they rewrote
> their application in Haskell/Caml with result Y".  Again, for my
> purpose I can't tell very long stories; but your message can give a
> bit more detail than one might actually give in a presentation.  The
> more concrete and specific, the better.  E.g. what, exactly, about
> using a functional language made it a win for you?
> 
> 
> If you just reply to me, with evidence of either kind, I'll glue it
> together (regardless of whether I find I can use it in my talks), and
> put the result on a Wiki page somewhere.  In both cases pointers to
> blog entries are fine.

This recent blog entry about PLT Scheme may be useful:
http://blog.plt-scheme.org/2007/11/getting-rid-of-set-car-and-set-cdr.html