The document discusses using domain specific languages to teach programming concepts to children through a turtle graphics language, provides examples of abstract syntax trees for different languages like a turtle language and Small Basic, and recommends resources for learning more about language design and domain specific languages including tryfsharp.org, a F# koans project, and Neil Danson's story about writing a C# compiler from scratch in 24 days.

1. 24 HOURS LATER Phillip Trelford, @ptrelford
#NCrafts Paris, 2015

2. THIS TALK IS *NOT*
About how to write a compiler the hard way
All theory
For the faint of heart

3. THIS TALK *IS*
ABOUT
Domain Specific
Languages
Abstract Syntax Trees
Parsing
Interpreters
Code Generation

4. LANGUAGE DESIGN (CONSIDERED
OPTIONAL)
Adhoc
•PHP
•JavaScript
•Scala
Copy&Delete
•Java
•J
•Go
Copy&Add
•C#
•F#
•Haskell

5. TO THE TURTLES CODE Phillip Trelford, @ptrelford
#NCrafts Paris, 2015

6. TURTLE LANGUAGE
repeat 10
[right 36 repeat 5
[forward 54 right
72]]

7. TURTLE AST
type command =
| Forward of arg
| Turn of arg
| Repeat of arg * command list

8. TWO GIRLS (5 & 7YRS) + TURTLE

9. SMALL BASIC
SAMPLE
Sub 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 detected
EndSub

10. SMALL BASIC AST
/// Small Basic expression
type 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

11. C# COMPILER IN 24 DAYS
Oh 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.

12. http://tinyurl.com/funbasi
c
FUN BASIC - WINDOWS
STORE APP

13. RESOURCES Phillip Trelford, @ptrelford
#NCrafts Paris, 2015

14. 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 __

15. TRYFSHARP.ORG

16. BUY THE BOOK

17. QUESTIONS?
Twitter: @ptrelford
Blog:
http://trelford.com/blog
Turtle: http://fssnip.net/nN