Functional Programming Fundamentals

Functional Programming Fundamentals

• 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 toF#  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
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  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