F# Eye for the C# Guy

F# Eye for the C# guy Leon Bambrick, secretGeek.net

F#... Do not be afraid.

I’m F #

functional

Purely functional…
Avoid
Side-
Effects!

Avoid
Mutation!

No Variables!
Only Functions!

Same input ->
Same output!

No Shared State

Why learn F#?

Do More With Less
“ If I was using F# I’d be done by now”
Why learn F#?

Do More With Less
See where C# and VB.net are headed
Why learn F#?

Do More With Less
See where C# and VB.net are headed
“ Learn one new language every year” (or two)
Why learn F#?

Moore’s Law Keeps Going!
Why learn F#?

But computers are not getting faster
Why learn F#?

Data Grows Quickly
But # of Dimensions Grows much faster!
And semi-structured data outgrowing structured
Entropy Increasing
Complexity is through the roof!

“ Software gets slower faster than hardware gets faster”
--Wirth’s Law

Some stuff is now cheap!
Ram
Disk
Cores
Some stuff remains expensive!
Time
Concurrency
Locking
Computer Economics is Changing

Some stuff is now cheap!
Ram
Disk
Cores
Some stuff remains expensive!
Real Time
Concurrency
Locking
Computer Economics is Changing

This tips the balance toward higher abstractions

Some Applications of F#
“ Computationally intensive” work
Map/Reduce over internets
Financial Analysis
Advertising Analysis
SQL Data Mining
XNA Games Development
Web tools, Compile F# to Javascript

Think About Game Programming

Game Programming Involves…
3D Animation
Rendering
Shading
Simulation (e.g. physics)
Collision Detection
AI Opponents

Genealogy of F # …
Theorem proving and ISWIM

Theorem proving and ISWIM begat:
ML “Meta Language”

ML “Meta Language”, which begat:
CAML

CAML, which in turn begat
OCaml
Oh!

CAML, which in turn begat
OCaml, which in turn begat
F#
... a sort of OCaml.net
(plus more)
Oh!

WTF # ?
First official functional language on .net

WTF # ?
Deep support thanks to Generics

WTF # ?
Assimilated by dev-div

WTF # ?
Assimilated by dev-div
Will ship in VS.next

Code!
Finally!

Code!
//F#
let a = 2

Code!
//F#
let a = 2
The ‘let’ keyword represents a binding between a value and an expression tree.

Code!
//F#
let a = 2
The ‘let’ blah blah blahblah blah blahblah blahblah blah blah blah blah blah blah.

Code!
//F#
let a = 2
//C# int a = 2 ≠

Code!
//F#
let a = 2
//C# //a function! static int a() { return 2; } More like

More Code!
//F#
#light
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); } } }

More Code!
//F#
#light
open System
let a = 2
Console.WriteLine a
More Noise Than Signal!

More Code!
//F#
#light
open System
let a = 2
Console.WriteLine a
Looks Weakly typed? Maybe Dynamic?

F# Yet Expressive

F# Yet Versatile

More Code!
//F#
#light
open System
let a = 2
Console.WriteLine a
Type Inference

let a = 2
let a = 3
error: FS0037: Duplicate definition of value 'a'
Immutable by default

let square x = x * x
> val square : int -> int
square 5
> val it : int = 25
simple function…

square 5
> val it : int = 25
simple function… Parameter

square 5
> val it : int = 25
simple function… “ Signature”

square 5
> val it : int = 25
simple function… Types are “inferred”

Discriminated union types
type NullableInt =
| Value of int
| Nothing of unit

type NullableInt =
| Value of int
| Nothing of unit
Wish C#/“O-O” had this.

type NullableInt =
| Value of int
| Nothing of unit
“ O-O” has discriminated union envy When the only tool you have is a hammer Everything looks like a nail

type NullableInt =
| Value of int
| Nothing of unit
“ O-O” has discriminated union envy When the only tool you have is a hammer Everything looks like a nail e.g. “Inheritance” ends up being used in places where it’s not a perfect fit…

type NullableInt =
| Value of int
| Nothing of unit
“ O-O” has discriminated union envy When the only tool you have is a hammer Everything looks like a nail e.g. “Inheritance” ends up being used in places where it’s not a perfect fit… ‘ Discriminated union types’ -- a better fit for some problems?

Another great tool is “pattern matching”

Another great tool is “pattern matching” “ Switch/Case” statements on steroids

Another great tool is “pattern matching” “ Switch/Case” statements on steroids “ method overloads” on crack

Discriminated unions example
type Weapon =
| Knife
| Gun
| Bomb

Lazy is a virtue
let lazy_square x =
lazy ( print_endline “thinking...“
x * x )
let lazy_square_ten = lazy_square 10
//first time: “thinking…”
Lazy.force (lazy_square_ten)
//second time: no thinking, just result
Lazy.force (lazy_square_ten)

Useful libraries Neat manual Awesome Samples

“ Empty” source file… 5 pages of help!

Make sure F# Interactive is running!

F# Interactive:
It’s the bomb!

F# Interactive:

msdn.microsoft.com/fsharp/

8 Ways to Learn
http://cs.hubfs.net
Codeplex Fsharp Samples
Books
ML

Acknowledgements
Cartman
Einstein
Dilbert
Alan Turing
Alonzo Church
Godzilla
Gears of war
John Hughes, Why Functional Programming Matters, http://www.math.chalmers.se/~rjmh/Papers/whyfp.html
Robert Pickering, Foundations of F#, http://www.apress.com/book/view/1590597575
Slava Akhmechet, Functional Programming For The Rest of Us, http://www.defmacro.org/ramblings/fp.html
Steve Yegge, Execution In the Kingdom of Nouns, http://steve-yegge.blogspot.com/2006/03/execution-in-kingdom-of-nouns.html
P. J. Landin, The Next 700 Programming Languages http://www.cs.utah.edu/~wilson/compilers/old/papers/p157-landin.pdf
Tim Sweeney, The Next Mainstream Programming Language , http://www.st.cs.uni-sb.de/edu/seminare/2005/advanced-fp/docs/sweeny.pdf
Tomas Petricek, F# Web Tools, Ajax Made Simple , http://www.codeplex.com/fswebtools
Don Syme, http://blogs.msdn.com/dsyme

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F# Eye for the C# Guy

by gueste3f83d on Sep 24, 2008

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F# Eye for the C# Guy — Presentation Transcript