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 think I qualify for this: I've been a long time C coder (and still do some), doing mostly UNIX/system stuff, most notably working on the FreeBSD kernel. I only recently (1 year, maybe one and a half) started learning Haskell so I still have fresh memories about my first feelings. One of the things that particularly impressed me was parametric polymorphism. As a C programmer, you tend to rewrite code to deal with linked lists every time you need one, adding next pointers to some structure of yours. This kind of things get boring fast (one could also use the BSD sys/queue.h macros, but they're ugly). So when I discovered about parametric polymorphism, and how you can have, for instance, a "length :: [a] -> Int" function working for any kind of lists, I was _very_ impressed. In a way, it is all perfectly logical to be able to have this kind of functions, since length doesn't need to know anything about what the list is holding, but it doesn't make it any less impressive for a C coder. Still on the parametric polymorphism topic, the Maybe datatype is what impressed me next. Everyone that has done some amount of C in his life knows how boring it is to have functions returning errors to the caller. If you're lucky, your function returns a pointer and can thus return NULL in case something went wrong. If your function returns an int and -1 has no meaning, you can use that too. But if you don't, it becomes messy quickly. It's even more annoying when the standard got it wrong, for instance the dreaded atoi() function. So, when I discovered the Maybe datatype, I was like a kid opening presents at christmas :-). The extreme simplicity of the definition of the Maybe datatype is impressive in itself, its convenience is as well, and the fact that it prevents a whole class of bugs by making it (nearly) impossible to ignore the fact that the function can fail is the cherry on top. Here are my $0.02 :-). I hope they'll be useful to you. This is mostly emotional and subjective stuff rather than technical, but I believe this is also what you're looking after. Maxime