24 HOURS LATER Phillip Trelford, @ptrelford#fsharpgotham NYC, 2015

THIS TALK IS *NOT*About how to write a compiler the hard wayAll theoryFor the faint of heart

THIS TALK *IS* ABOUTDomain Specific LanguagesAbstract Syntax TreesParsingInterpretersCode Generation

LANGUAGE DESIGN (CONSIDERED OPTIONAL)

Adhoc• PHP• JavaScript• Scala

Copy&Delete• Java• J• Go

Copy&Add• C#• F#• Haskell

TO THE TURTLES CODE

Phillip Trelford, @ptrelford#fsharpgotham NYC, 2015

TURTLE LANGUAGErepeat 10 [right 36 repeat 5 [forward 54 right 72]]

TURTLE ASTtype command = | Forward of arg | Turn of arg | Repeat of arg * command list

THINGS YOU SHOULD NEVER DO Custom Operators Funny picture

TWO GIRLS (5 & 7YRS) + TURTLE

SMALL BASIC SAMPLESub Init gw = 598 gh = 428 GraphicsWindow.BackgroundColor = "DodgerBlue" GraphicsWindow.Width = gw GraphicsWindow.Height = gh color = "1=Orange;2=Cyan;3=Lime;" size = "1=20;2=16;3=12;" passed = 0 cd = "False" ' collision detectedEndSub

SMALL BASIC AST/// Small Basic expressiontype expr = | Literal of value | Identifier of identifier | GetAt of location | Func of invoke | Neg of expr | Arithmetic of expr * arithmetic * expr | Comparison of expr * comparison * expr | Logical of expr * logical * expr

/// Small Basic instruction type instruction = | Assign of assign | SetAt of location * expr | PropertySet of string * string * expr | Action of invoke | For of assign * expr * expr | EndFor | If of expr | ElseIf of expr | Else | EndIf | While of expr | EndWhile | Sub of identifier * string list | EndSub | Label of label | Goto of label

C# COMPILER IN 24 DAYSOh Yes! Neil Danson (aka The Do)

Now, I didn’t do any compiler theory in uni, I’ve never written a compiler before and I’ve only ever looked at Reflection Emit in anger. But despite these limitations I have a fairly capable C# 0.5 compiler (in that it is a subset of the C# 1 compiler). Which means you can do it too – it took me less than a month.

http://tinyurl.com/funbasic

FUN BASIC - WINDOWS STORE APP

FUN SHARP RUNNING ON RASPIAN http://github.com/ptrelford/fu

nsharp

RESOURCES Phillip Trelford, @ptrelford#fsharpgotham NYC, 2015

F# KOANS[<Koan>]let SquareEvenNumbersWithPipelineOperator() =(* In F#, you can use the pipeline operator to get the benefit of the parens style with the readability of the statement style. *)

let result = [0..5] |> List.filter isEven |> List.map square AssertEquality result __

TRYFSHARP.ORG

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QUESTIONS?

Twitter: @ptrelfordBlog: http://trelford.com/blogTurtle: http://fssnip.net/nN