F# Ignite presentation realized at DotNetArchitects Day 2010, in Brazil.

1. {
F#ture
and F#nctional Programming

2. Rodrigo Vidal
Twitter: @rodrigovidal
Blog: www.rodrigovidal.net
 Focus on Software Architecture
 F# and IronRuby/Ruby enthusiast.
 .NetArchitects – Rio de Janeiro , user group member
 Professional Scrum Developer
Quem sou eu?

3.  Old Paradigm
 52 years old
 Ignored by MainStream until now.
Functional Programming

4.  New Challenges
 Process big amount of data
 Escale to Clusters and Cores
Functional- Why now?

5.  Think out of the box
 Functional Programming is “safe”
 MultiCore and Cloud Computing applications
 Functional Programming is obtaning market
Why learn another language?

6. Imperative Vs. Declarative
What rather than How

7. Another way of thinking
List<string> res = new List<string>();
foreach(Product p in Products) {
if (p.UnitPrice > 75.0M) {
res.Add(String.Format("{0} - ${1}",
p.ProductName, p.UnitPrice));
}
}
var res = from p in Products
where p.UnitPrice > 75.0M
select string.Format("{0} - ${1}",
p.ProductName, p.UnitPrice);
return res;

8. Functional Paradigm
 Immutable Data
 Ability to compose functions
 Functions can be thread as data
 Lazy Evalution
 Pattern Matching

9. Immutability
“Values are immutable by default”
let x = 3
let x = 4
error FS0037: Duplicate definition of value ‘x'

10. Side-Effects
 A side effect
 Modifies some state
 Has observable interaction with calling functions
 Has observable interaction with the outside world
 Example: a function or method with no return value
let mutable x = 3
let y = x*3
x <- 4
let z = x*3

11. Composing Functions
f(x) = 3x+2
g(y) = 4y-1
Z = g(f(2)) = ?
f(x)
g(x)
let f x = 3*x + 2
let g y = (4*y) - 1
let z = g(f(2))

12. #Inception
Lambda
Calculus
LISP ML Ocaml Haskell F#

13. Languages Evolution
0
2
4
6
8
10
12
0 2 4 6 8 10 12
Usefulness
Safety
C#
Nirvana
Haskell
LINQ
C#, VB,
Java
LINQ Nirvana
Haskell
http://channel9.msdn.com/posts/Charles/Simon-Peyton-Jones-Towards-a-Programming-Language-Nirvana/
C#, VB, Java, C are
imperative
programming
languages. Very
useful but can change
the state of the world
at anytime creating
side effects.
Nirvana!
Useful and
Safe
Haskell is Very Safe, but
not very useful. Used
heavily in research and
academia, but rarely in
business.
F#

14. What´s is F#?
 Functional language developed by Microsoft Research
 By Don Syme and his team, who productized Generics
 Based on OCaml (influenced by C# and Haskell)

15. F# Evolution
2002
F# language
design started
2005 January
F# 1.0.1 releases
to public
2005 November
F# 1.1.5 with VS
2005 RTM support
2009 October
VS2010 Beta 2,
CTP for VS2008
& Non-
Windows users
2010
F# is
“productized”
and baked into
VS 2010

16. F# 2.0
Functional + Objects + .NET +
Async + Parallel + Interactive + Scripting

17. F# 2.0
//F#
open System
let a = 2
Console.WriteLine a
//C#
using System;
namespace ConsoleApplication1
{
class Program
{
static int a()
{
return 2;
}
static void Main(string[] args)
{
Console.WriteLine(a);
}
}
}

18. let fim = “Obrigado”