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ilolu
Are there any good set of videos to learn Haskell ? Or which book should I start with. I don't have much experience in Functional Programming.
agumonkey
I believe jumping right into Haskell, unless you're already fond of recursion, is a bit too stiff. Maybe try to read SICP, it will expose you to the functional programming principles that lead to Haskell (strict vs lazy evaluation) which he mostly makes more concise and expressive.

Here's a playlist of a lecture session for HP employees by the authors of the book : http://www.youtube.com/playlist?list=PLB63C06FAF154F047

Here's the book http://mitpress.mit.edu/sicp/ ( alternate formatting texinfo http://www.neilvandyke.org/sicp-texi/ , pdf http://sicpebook.wordpress.com/ )

bestham
I find that this rather old video from OSCON 2007 by the incredible Simon Peyton Jones (of F# and GHC) is the most inspiring Haskell video there is. It uses the X window manager XMonad as the basis to explain many important concepts of Haskell and testing (QuickCheck). It is self contained and no previous knowledge of Haskell is needed:

http://blip.tv/oreilly-open-source-convention/oscon-2007-sim...

Watabou
Wow, thanks for this, it's exactly what I needed.

I started from LYAH and the only thing missing from it were some exercises so I could retain the information that was presented in each chapter. Otherwise, it's a fantastic book.

WasimBhai
Why should I learn Haskell? Will it help me professionally, or help me being a better programmer?
Dewie
You could Google that exact question. It has been answered a lot of times on StackOverflow and other sites.
Peaker
Because you will find it is the best tool for many programming jobs.
shoki
> Why should I learn Haskell?

http://stackoverflow.com/questions/1604790/what-is-haskell-a...

For my own 2-cents, once I learned QuickCheck[1] and Parsec[2], I found myself slowly rewriting them for every language I program in.

> Will it help me professionally?

Speaking as another professional, probably not.

I love Haskell, but my colleagues can't deal with it. They can't write it. They don't know functional programming. And to be entirely honest, they will never understand Monoids, Monads, or macro-hacking.

> ...Help me being a better programmer?

Maybe. If you like already like to think of software axiomatically, then yes, it will make you will make you think of software more conceptually.

But honestly, getting javascript, ruby and go under your belt will also make you think differently about software, and those are more practical languages.

[1] http://en.wikipedia.org/wiki/QuickCheck [2] http://www.haskell.org/haskellwiki/Parsec

dschiptsov
I really like the amount of nonsense.)

It begins with head is a mistake! It should not be in the Prelude. Other partial Prelude functions you should almost never use include tail, init, last, and (!!). From this point on, using one of these functions on a homework assignment will lose style points!

And here is a proposal:

  data NonEmptyList a = NEL a [a]

  nelToList :: NonEmptyList a -> [a]
  nelToList (NEL x xs) = x:xs

  listToNel :: [a] -> Maybe (NonEmptyList a)
  listToNel []     = Nothing
  listToNel (x:xs) = Just $ NEL x xs

  headNEL :: NonEmptyList a -> a
  headNEL (NEL a _) = a

  tailNEL :: NonEmptyList a -> [a]
  tailNEL (NEL _ as) = as
Dear sirs, a List is a recursive data structure by definition. Non-recursive List is an unimaginable nonsense. What was made here with a name of safe(!) NonEmptyList is some ugly Pair with lots of syntactic noise.

How could you get the last element from your NonEmptyList? How could you tell how many elements in it?)

But, of course, never ever use these ugly unsafe lists - they might be empty! Use safe NonEmptyList because in Haskell everything is safe. And never try to think what the fuck you are reading.

Peaker
A better solution is length-encoded lists (often called Vectors):

  data Vector length a where
    Empty :: Vector 0 a
    Cons :: a -> Vector n a -> Vector (1 + n) a
But Haskell isn't very good at such encodings. Type-level computation is often not worth it.

That said, even NonEmptyList is sometimes useful. For example, some Prelude functions could use it:

  group :: [a] -> [NonEmptyList a]
Making common idioms like:

  map head . group ...
Safe again.

Not sure what you mean by:

> How could you get the last element from your NonEmptyList? How could you tell how many elements in it?) Exactly two.

  import Data.Monoid
  import Data.Maybe

  lastNel :: NonEmptyList a -> a
  lastNel (NEL x xs) = fromMaybe x . getLast $ mconcat $ map (Last . Just) xs

  lengthNel :: NonEmptyList a -> Int
  lengthNel (NEL x xs) = 1 + length xs
dschiptsov
But these are solutions for some Array of unknown size or some abstract collection - why to call it a List? For a List the notion of the-empty-list is essential.
tome
> List is a recursive data structure by definition

What's the justification for that assertion?

Ashuu
Is it only for UPENN students?
mcintyre1994
I really wanted to learn functional programming when my university offered it, but unfortunately it's crunched in a horribly busy term and I'm not willing to risk core modules for it if I end up struggling.

That said, I really do want to learn it and find MOOCs a really useful tool, if anybody has any suggestions for any they've used (or the one linked, I'm unclear if that's for students at that university only) that'd be awesome!

mcintyre1994
Thanks, it's a shame the content is only available when it's running because again the timing isn't great. I'll definitely check it out though.
xzel
I took this class last semester. Learned a lot. Brent was a great professor and is a great guy.