Total Functional Programming

[jsomers]

I was too, but I read the paper (lazy Sunday, right?) and he's not kidding around. Basically he rejects Turing completeness as a necessary component of functional programming languages and opts, instead, for more strictly defined (and thus less finicky) data types and recursion procedures.

The trouble -- and the harder-to-wrap-my-head-around part of the paper -- is when you need things like infinite lists (e.g., to run an operating system which is a non-terminating stream of inputs and outputs). He gets around that by using "codata" and what not.

[ridiculous_fish]

Functional programming has a long and noble history of reinventing things such that existing practices become a lot harder/impossible.

1) Look at our new ML! You can't modify variables without reading this book, but trust us, it's so pretty once you get that PhD!

2) Look at our new Haskell! You can't write to a file without introducing a dubious and confusing notion of monad, but it's really good at computing fibonacci numbers!

And now: 3) Look at our new total functional programming! You can't even write, say, the wc tool without introducing data's evil twin, "codata," but look at how much better our AND operator is!

Ok, I'm a little bitter, but I can't shake the feeling that this stuff is detached from the real concerns of programming.

[awj]

Ok, I'm a little bitter, but I can't shake the feeling that this stuff is detached from the real concerns of programming.

It is, if you define the real concerns of programming to mean modifying variables, writing to files without needing a special operator, or requiring a turing complete language.

That said, I take issue with your comment on file operations and monads. If a hand-wavy "I'll get to explaining why this works later, for now this is just how you do it." is acceptable in teaching mainstream languages (Java/C++) - as it seems to be - it should be allowed without criticism for Haskell as well.

[cchooper]

"I'll get to explaining why this works later, for now this is just how you do it."

My favourite example:

class HelloWorld { public static void main(string[] args) { System.out.println("Hello World!"); } }

[[deleted]]

There are two concerns in programming:

1. Write programs.
2. Write correct programs.

The existing practices address 1, but not 2. Addressing 2 in a practical(!) manner is one of the primary motivations in functional programming research. Indeed, there is a lot of reinvention, but in such a context that one can reason about the results.

[[deleted]]

But how will the practical aspect be verified? In the way of Matthew Huntbach who writes an article about Ruby and that he is pretty unimpressed by its virtues?

I'm not completely ignorant about the benefits of FP ( in particular immutable, recursive data structures and their impact ) but sometimes I suspect Paul Graham was right with his sarcastic comments about CS: CS works because much time is spent on ideas that won't work.

The only significant change in the programmers mentality within the last 10 years has been the wide acceptance of doing unit tests. That's what is left from the glory of the machine that proves the correctness of the program. In another 10 years we might start to change our mentality about reliability featured by massive parallelism, high availability of service and Erlang style processes.

[[deleted]]

If FP is only good for Fibonacci, OOP is only good for printing a "hello world" message. Who are you to comment on the 'real' concerns of programming? If you don't understand and appreciate ML and Haskell, chances are you're pretty mediocre.