Haskell
Bart Massey
Bart Massey
Donnie Berkholz
John Sechrest
tim Bauman
Tim Savard
Jesse Hallett
Haven Hash
Iseff
Maurice Dodik
Jek
Phil Tomson
Sam Keen
What is haskell? And why should I care?
Bart thinks that Haskell is the next big thing.
Why? isn't C++ enough for anything?
Haskell is a functional programming language.
We build pieces that are so modular, so that mix and match is trivial.
What do you give up?
-Global Variables...
- Variables all together....
What is the difference between a name for a value vs a variable?
Variable is the mapping from a name to a location.
There is no location in haskell
In trade, you get modularity.
GHCI -
interactive , incrementally compiled language
It does static type checking.
no type declarations. The program guesses the type.
Open source community has adopted Haskell.
Haskell programming can be harder , because the lack of variables.
Indentation does matter
No brackets
Not end markers
it is case senstive
it does lazy evaluation
you can do type annotation
emacs count.hs
main = do
printCount 10
where
printCount 1 = putStrLn 1
PrintCount n = do
putStrLn (show n)
printCount ( n - 1 )
gch count.hs
1,2,3 A list - First class objects
head 1,2,3
tail 1,2,3
let count x = x: ( count (x + 1) )
let y = count (1)
head y => 1
take 3 y => 1,2,3
tail y => infinite list
Is there a way to track what code is run.
there is a profiler
Haskell is 15 years old.
How does haskell performance work
Ocamel ?
C?
As a matter of practice 2-200 Times slower than C.
Language shootout
Darcs is a source code control in haskell
WASH - Web in haskell
web apps in haskell
you get concurrency for free
tile :: Int -> Int -> a -> [a]
Currying
Tile _ _ [] = []
tile n o s =
let cur = take n s
rest = drop ( n - o ) s in
cur : ( tile n o rest)
peak s = ( maximum . map abs . map avg . tile 3 2 ) s
. means composition
Guarded patterns
Lambda calculus
Y combinator -> The function that expresses recursion as a foundation.
If you know ML , it does help.
A program you want to write quickly
pretty sure it is right the first time
get reasonable performance
Access to an active programming community
Resources
-----------
http://www.haskell.org
http://www.haskell.org/tutorial
svcs.cs.pdx.edu/git/ppg.git
truelevel.git
http://svcs.cs.pdx.edu/darcs/minichess
http://darcs.net/DarcsWiki
