1. Installation and exercises
HASKELL
Installation and exercises

2. Installation http://www.haskell.org Main Page  Download Haskell
Haskell Engine + GHCi
In Windows: Also WinGHCi
GHCi: Haskell Compiler/Interpreter

3. GHCi

4. Interpreter: Try it out!
Math Operations and Functions
2 + 2
10^2
log(10)
Lists
[1, 2, 3]
[1..10]
[“x”, ”y”, ”z”]
[‘x’, ’y’, ’z’]
Variable Assignment
let x = 5 in x^2 + 2*x + 4

5. Running Haskell Script Files
Create a new file, “HelloWorld.hs”
main = do putStrLn "Hello, world!"
Change the current directory:
:cd <Directory of HS file>
Load the file:
:load HelloWorld.hs
Run the file:
main

6. Running Haskell Files

7. Basic List Manipulation
Get first element: head <list>
Get last element: tail <list>
Get nth element: <list> !! N
Get first n elements: take n <list>
Remove first n elements: drop n <list>
Length of list: length <list>
Sum of numbers: sum <list>
Product of numbers: product <list>
Append lists: <list1> ++ <list2>
Reverse list: reverse <list>

8. Functions in Haskell Prefix Operations: Operation before operands.
In Math: f(x,y) + z
In Haskell: f x y + z
Function has higher priority
In Math: f(x,y+z)
In Haskell: f x (y+z)
Function of functions
In Math: f(x,g(y))
In Haskell: f x (g y)
Recursion is highly encouraged

9. Defining functions Defined in a Haskell script file Example:
The “=“ operator
Arguments
Example:
double x = x + x
squared x = x * x
hypothenuse x y = sqrt(x^2 + y^2)

10. Implicit Grouping Used when defining functions
Same spacing/tabbing to denote groups
hypothenuse2 x y = sqrt(z)
where
z = x2 + y2
x2 = x^2
y2 = y^2

11. Exercises Fix the syntax error and try the following program:
N = a ’div’ length xs
where
a = 10
xs = [1,2,3,4,5]

12. Exercises
Write two possible definitions of the ‘lastOne’ function that selects the last element of a list.
Write two possible definitions of an ‘init’ function that removes the last element of a list.
Write a function that receives a list and returns a list of the original values of the list plus two

13. Exercises Write a function for the factorial operation
Write a function that receives a numerical user input and returns the factorial of that number
To obtain user input:
X <- readLn
Write a function that receives a numerical user input ‘x’ and returns a list from 0 to x

14. Exercises
EXTRA: Write a function that calculates the nth number of the Fibonacci sequence
Fibonacci numbers:
f(n) = f(n-1) + f(n-2)
f(0) = 1
f(1) = 1