Functional Programming Is Hard, That's Why It's Good

When I finally come to create my own map of some small island of history of computing, namely "type systems", I was thrilled, no less.

The superheroes are among us, I think. ;)

Joke aside - I don't want to write essays here, so I'm gonna try to make a hopefully brief point.

I -know- your essay was well-intentioned, and believe me, so is my reaction, after having written software for a living for nearly 15 years...

Rather than to expound - let me ask you - do you know of Martin Fowler? I can get Graham and his cult-like persona has ensnared you/others somewhat in his FP-Kool-Aid cult :D... but read Fowler for a bit of balance too.

Your intention was actually awesome - you want to illustrate a general principle, e.g. an abstraction, that thinking via and writing through a functional paradigm/language makes you a better programmer. Is that "true" to the extent you and a bunch of other FP-evangelists claim? Why, yes it is! So is learning assembly language, or Brainf*ck for that matter....

Why I mentioned and really enjoy reading Fowler's non-imposing, well-argumented style of writing is because he effectively does, what you bravely attempt to do here, convey a general principle about _programming languages_, except he does it expertly, whereas you do it naively, despite the good intention. To get what I'm saying, surf over to www.amzn.com, and get yourself a copy of Fowler's Domain Specific Languages.

Upon reading that book, heck, even half way, you soon come to the same realization that what one of the other repliers to my original rant has come into some time ago - we are ultimately discussing various paradigms/philosophies of thinking. Not ONE single or multiple paradigms that are tailored to your particular way of thinking or that you are "hard wired" for (which I find hard to believe, but I'll grant some 'nature vs nurture' arguments here too), makes you or anyone else, me included, necessarily a 'better' programmer... I'd go as far as saying that it's probably your personality, mental/emotional states you experience on a daily basis while glued to your PC, that have you be more or less effective at programming, e.g. you're a 'perfectionist/procrastinator', most common among programmers, or you're extreme and reckless and use inadequate tools to just conjure something up, looking to get 'promoted' and it blows up a few months later or BSOD's in a demo to the board of directors....

This has been said over and over, and for some reason, it doesn't sink in - there is no silver bullet, there is no 'better/worse' programmer - unless you count lines of code produced per day as a 'productivity measure', hardly a clever measure of anything...

Back to your essay - I'd much rater you embark on the topic of DSLs, rather than using CL as a platform to write a DSL in - which is -fine- except maybe people who are unfamiliar with Lisp's syntax, e.g. domain experts, can relate to a specific, external DSL better than they can relate to a LISP based DSL...

Think of teaching a DSL to a ... I dunno, a postal worker who examines mail rejects that didn't pass the OCR phase. You could construct a DSL specific to that purpose. It would be relevant and useful and increase the worker's productivity.

On the flipside, teaching him Lisp, such that he can learn a DSL designed inside of Lisp, would be a pain in the ass...

DSLs, e.g. macros, are one of the highly touted benefits of Common Lisp, which I actually like, because of its multiparadigm ('dirty') nature...

Anyway, I don't really want to indulge here - I think if you are serious about writing something, which I believe you are - be as balances as you can be, and never throw ANYONE under the bridge - including people who have only coded VB in their life.... You are either on board w/all people, or you're alone.

Smugness about a particular paradigm is something I'd stay away from, as well as people who hypnotize you with their eloquence and "successes" (financial or otherwise) into thinking that they've discovered the next best thing since sliced bread.....

This is why, as much as I like my Macbook, I still think Apple's a cult, and that Linux will eventually prevail, even on mobile platforms, tablets, etc.

Peace.

... OOP is inherently less useful that FP ...

Is it that hard to see different uses for different languages? Original BASIC was neither OO nor FP and came after both. Still it satisfied a particular need. C++ is the worse programming language in the world, except for all the others - in the domain it is used in.

Let's take a simple example, a to-do list. Abstracted out to its essentials (a piece of paper), the to-do list is exclusively state. Add a task, complete a task.

Now, I can write a program that manages a to-do list in a functional language. There are two options. (Let's assume this is a web app.) First, I can make the client manage the state. Each time they use the application, they bookmark the last page. This is obviously inconvenient, but it's pure. Every input has a distinct output. Send the entire to-do list and what you wish to add or complete as input, receive an update copy of the state in return. It's always immutable state. It's also inconvenient if you ever want to use this on another computer.

So, like most to-do lists, we use a database on the server side to manage the state of the application. However, you've lost the entire benefit of immutable state! You are not guaranteed to get the same output given an input. We're back to square one, aren't we? What's functional about mutable state?

Now, in a subset of programs, eliminating mutable state is beneficial. 99% of scientific programming would be best served by FP. However, I've never seen an answer to how we can still call any system functional once we add a database.

And at that point, why aren't we using a language that is bad at what we expressly need in the first place?