F# Eye for the C# Guy
Post on 02-Jul-2015
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F# Eye for the C# guyF# Eye for the C# guy
Leon Bambrick, secretGeek.netLeon Bambrick, secretGeek.net
F#...F#...
Do not be afraid.Do not be afraid.
hello
I’m F#
functional
Purely functional…
Avoid Side-
Effects!
Purely functional…
Avoid Mutation!
Purely functional…
No Variables!
Only Functions!
Purely functional…
Same input ->Same output!
No Shared StateNo Shared State
Purely functional…Purely functional…
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– “If I was using F# I’d be done by now”
• See where C# and VB.net are headed
Why learn F#?
• Do More With Less– “If I was using F# I’d be done by now”
• 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!– Time–Concurrency– Locking
Computer Economics is Changing
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
Genealogy of F# …
• Theorem proving and ISWIM begat:
–ML “Meta Language”
Genealogy of F# …
• Theorem proving and ISWIM begat:
–ML “Meta Language”, which begat:
• CAML
Genealogy of F# …
• Theorem proving and ISWIM begat:
–ML “Meta Language”, which begat:
• CAML, which in turn begat
–OCaml
Oh!
Genealogy of F# …
• Theorem proving and ISWIM begat:
–ML “Meta Language”, which begat:
• 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#?
• First official functional language on .net
• Deep support thanks to Generics
WTF#?
• First official functional language on .net
• Deep support thanks to Generics
• Assimilated by dev-div
WTF#?
• First official functional language on .net
• Deep support thanks to Generics
• 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##lightopen Systemlet a = 2Console.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##lightopen Systemlet a = 2Console.WriteLine a
More Noise Than Signal!
More Code!
//F##lightopen Systemlet a = 2Console.WriteLine a
Looks Weakly typed?Maybe Dynamic?
F#?
F#
F# Yet Expressive
F#
Yet Versatile
More Code!
//F##lightopen Systemlet a = 2Console.WriteLine a
Type Inference
let a = 2let 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…
let square x = x * x
> val square : int -> int
square 5
> val it : int = 25
simple function…
Parameter
let square x = x * x
> val square : int -> int
square 5
> val it : int = 25
simple function…
“Signature”
let square x = x * x
> val square : int -> int
square 5
> val it : int = 25
simple function…
Types are “inferred”
Discriminated union typestype NullableInt =
| Value of int
| Nothing of unit
Discriminated union typestype NullableInt =
| Value of int
| Nothing of unit
Wish C#/“O-O” had this.
Discriminated union typestype NullableInt =
| Value of int
| Nothing of unit
“O-O” has discriminated
union envy
When the only tool you have is a
hammerEverything looks
like a nail
Discriminated union typestype NullableInt =
| Value of int
| Nothing of unit
“O-O” has discriminated
union envy
When the only tool you have is a
hammerEverything looks
like a nail
e.g. “Inheritance” ends up being used in places
where it’s not a perfect fit…
“O-O” has discriminated
union envy
Discriminated union typestype NullableInt =
| Value of int
| Nothing of unit When the only tool you have is a
hammerEverything 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
Pattern Matching
type Weapon =
| Knife
| Gun
| Bomb
//block any weapon!let block w = match w with | Knife | Gun -> disarm w | _ -> difuse w
block Gunblock Knifeblock Bomb
Pattern Matching
type Weapon =
| Knife
| Gun
| Bomb
//block any weaponlet block w = match w with | Knife | Gun -> disarm w | _ -> difuse w
block Gunblock Knifeblock Bomb
Lazy is a virtuelet 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 resultLazy.force (lazy_square_ten)
Lazy is a virtuelet 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 resultLazy.force (lazy_square_ten)
Useful libraries
Neat manual
AwesomeSamples
“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/
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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