Haskell is a pure functional programming language that is statically typed and implements immutable data structures. It uses recursion extensively in place of loops. Some key features include: - Functional programming with immutable values and functions as first-class citizens - Static typing with type inference - Recursion instead of loops for iteration - List comprehensions and pattern matching It has compilers like GHC and interpreters like Hugs. Code examples demonstrate list handling, recursion, and functional concepts like currying, partial application, and let/in bindings. Haskell has advantages for learning functional programming but also has disadvantages like initial complexity and lack of performance of other languages.

1. Haskell
By Jackson Oliveira
@cyber_jso

2. The First Version Is From Nineties

3. In The Beginning, It Was Just to Learn

4. But With The Principal Functional
Programming Resources
Curryng Partial Processing
FUNCTION COMPOSITION
Monads Lambda

5. So, What is Haskell Then?
• A Pure Functional Language.
• It’s Static Typed.
• It implement the immutable
concept.

6. Complex Things Looks Like Easy

7. It Uses a Lot of Recursion
There is
No Loops

8. How Can We Compile Haskell Code?
• Glaskell Haskell Compiler
• NHC98
• Hugs (Intepreter)
• LHC

9. Lets See Some code

10. Distributing an Application
module Main where
main = putStrLn "Hello Functional Society!“
In the command line:
> ghc -o hello main.hs
> ./hello
> Hello Functional Society!

11. List Handling
> 0:[1,2] > map Char.toUpper "Hello World"
[0,1,2] "HELLO WORLD“
> zipWith „ (++) [“foo”, “bye”] [“bar”, “ bye”]
> 5:[1,2,3,4] [“foo bar”, “bye bye”]
[5,1,2,3,4]
> foldr (+) 0 [3,8,12,5]
28
> foldl (+) 0 [3,8,12,5]
28

12. Recursion
module QuickSort where
> quickSort [3, 1, 4]
quickSort [] = [] > [1, 3, 4]
quickSort [x] = [x]
quickSort (x : xs) = (quickSort less)
++ (x : equal)
++ (quickSort more)
where less = filter (< x) xs
equal = filter (== x) xs
more = filter (> x) xs

13. The Previous Recursion Wrote in C
void qsort(int a[], int lo, int hi)
{
int h, l, p, t;
if (lo < hi) {
l = lo;
h = hi;
p = a[hi];
do {
while ((l < h) && (a[l] <= p))
l = l+1;
while ((h > l) && (a[h] >= p))
h = h-1;
if (l < h) {
t = a[l];
a[l] = a[h];
a[h] = t;
}
} while (l < h);
a[hi] = a[l];
a[l] = p;
qsort( a, lo, l-1 );
qsort( a, l+1, hi );
}
}

14. Let/in
letExample a b =
let testValue = (+) a b
in (((+) testValue 1),
((-) testValue 1))

15. Curryng
> max 5 4 > max 4
4 > [function of max] 5
5
> f(x + y/2) = 2
>
5

16. Partial Processing
> add x y = x + y
> addOne = add 1
> addOne 2
3

17. Wild Cards
> caseExample x = > [1 .. 10]
case x of [1,2,3,4,5,6,7,8,9,10]
0 -> 1
1 -> 5 > myFunction 3 = 3
2 -> 2
_ -> -1 > myFunction _ = 0

18. Advantages in Learn Haskell?
• Open your mind!
• Make your code cleaner
• It has a community supporting
• You have the control!

19. Ecosystem
• Web Frameworks! • Persistence
Frameworks
• Test Frameworks.
• Web Servers
• Concurrency and
STM Frameworks

20. Disvantages
• It can Looks like complex in the
beginning.
• It isn’t performatic
• Doesn’t implement some bstractions
like other functional languages

21. Thank You!
Haskell
By Jackson Oliveira
@cyber_jso