1. Functional
Programming
{ Introduction to F#

2.  Oleksiy Tereshchenko
 Principal consultant at Neudesic
 10 years experience in Custom Application
Development and Connected Systems
About Presenter

3.  Introduction to F#
 F# fundamentals
 Demo
& Questions
Agenda

4.  Functional programming is a style of
programming that emphasizes the evaluation
of expressions, rather than execution of
commands. The expressions in these languages
are formed using functions to combine basic
values. [Hutton ed. 2002]
Definition

5.  LISP - by John McCarthy in 1958
(based on the lambda calculus theory)
 ML - by Robin Milner in 1970s
(notion of types and types inference)
 OCaml – in 1996
(pragmatic extension of ML, combination of object-oriented and functional
programming)
 Haskell – in 1990s
(mathematical purity and elegance)
 Erlang – in 1986
(simplified concurrent programming)
History

6.  LINQ
 SQL
 XAML
 XSLT
Modern declarative
technologies

7.  Business Logic Layer of Enterprise Systems
Best fit for functional
programming

8.  Makes you and your team productive
Key reason for coding in
functional Style

9.  Express Abstraction (hide how code executed and specify what needs to be
achieved)
 Reuse of patterns
 Reduce impact of requirements change
 Deterministic flow
 Asynchronies flow
 Run concurrently on multiprocessor core
 Simple testing
F# designed to solve
problems

10.  Functional Programming
 Function Values
 Function Composition
 Immutability
 Recursive Functions
 Type Inference
 Lazy Evaluation
 Tail Recursion
 Sequences
 Imperative Programming
 Object-Oriented Programming
 Asynchronous Workflows
 Parallel Programing
F# offers

11. F# Fundamentals

12. let number = 1
let Number : int = 1 (F# is case sensitive)
let number = 1 (will fail compilation, since = is binding operation and not assignment )
Variables

13. let main (argument) =
printfn “Hello, World %s ” argument
0
let square x = x * x
let rec factorial x =
if x <= 1 then
1
else
x * factorial (x-1)
Functions

14. let isOdd x = (x % 2 = 1)
let describeNumber x =
match isOdd x with
| true -> printfn “x is odd”
| false -> printfn “x is event”;;
Pattern Matching

15. let x = Lazy<int>.Create(fun () -> printfn
"Evaluating x…"; 10)
let y = lazy (printfn "Evaluating y…"; x.Value +
x.Value);;
y.Value
Lazy evaluation

16. let sequenceOfNumbers = seq {1 .. 5}
sequenceOfNumbers |> Seq.iter (printfn "%d")
Sequences

17. while
let mutable i = 0
while i < 5 do
i <- i + 1
printf “i = %d” i;;
for i = 1 to 5 do
printf “i = %d” i;;
Looping constructs

18. try
try
failwithf "Error!"
with
| :? NotSupportedException ->
reraise()
| ex -> printfn "Exception caught: %s"
ex.Message
finally
printfn "finally block"
Exception management

19. Demo