The document is a summary of the Metasepi team meeting #19 focusing on ATS application development on Arduino. Key discussions included an overview of the Metasepi operating system, the ATS language, and demo codes related to Arduino-ATS, highlighting features like dependent types and error handling at compile time. Additionally, resources and links to related projects and user groups were provided for further exploration of the topics discussed.

1. Metasepi team meeting #19:
ATS application on Arduino
Kiwamu Okabe @ Metasepi Project

2. Demo: ATS on Arduino Uno
☆ http://nico.ms/sm24680530
☆ https://github.com/fpiot/arduino-ats
☆ Without any GC, and any malloc

3. Demo: Arduino Uno
☆ MCU: ATmega328
☆ Flash Memory: 32 KB
☆ SRAM: 2 KB
hhhttttttppp::://////aaarrrddduuuiiinnnooo...cccccc///eeennn///MMMaaaiiinnn///AAArrrddduuuiiinnnoooBBBoooaaarrrdddUUUnnnooo

4. Demo: LCD Shield
☆ LinkSprite 16X2 LCD Keypad Shield
☆ 16x2 LCD
☆ HD44780 compatible
http://store.linksprite.com/linksprite-16x2-lcd-keypad-shield-for-arduino-
version-b/

5. Demo: Software Architecture

6. Demo code: main.dats

7. Demo code: lcs.sats

8. Demo code: lcs.dats
☆ We don't read it, today.

9. Agenda
☆ [0] ATS application demo
☆ [1] What is Metasepi?
☆ [2] How to create Metasepi?
☆ [3] What is ATS language?
☆ [4] Let's read the demo code
☆ [5] Japan ATS User Group

10. [1] What is Metasepi?
http://metasepi.org/
☆ Unix-like OS designed by strong type.
☆ We want to use Metasepi OS for daily
desktop usage (e.g. web browser,
programming, office suite, ... etc.)
☆ We have surveyed may functional
languages (e.g. Haskell, OCaml,
MLton, ... etc.)

11. Kernel developer wants type
☆ Kernels are developed with C.
☆ We should design kernel with the
greatest care.
☆ C language is unsafe!

12. Kernel Bug #1: Buffer overrun
☆ Pointer to array doesn't know the
length.

13. Kernel Bug #2: Page fault
☆ Page fault in user space => SEGV
☆ Page fault in kernel space => Halt!

14. Kernel Bug #3: Weak type
☆ Lots of (void *) and unsafe coercion.
☆ NetBSD kernel uses it 45130 times!
$ pwd
/home/kiwamu/src/netbsd/sys
$ grep "void *" `find . -name "*.c"` | wc -l
45130
☆ Kernel developers frequently use
(void *) for flexibility. It's realy BAD, but
there is no other option.

15. [2] How to create Metasepi?
☆ Scratch or Rewrite

16. Snatch-driven development
http://en.wikipedia.org/wiki/Snatcher

17. Which language should we use?
☆ ATS http://www.ats-lang.org/

18. [3] What is ATS language?
http://www.ats-lang.org/
☆ Syntax like ML
☆ Dependent types
☆ Linear types
☆ Without any runtime
☆ Optional GC
☆ Developed at Boston University

19. ATS compile flow

20. [4] Let's read the demo code
Start from main.dats.
arduino-ats
|-- DATS
| `-- lcd.dats
|-- SATS
| |-- arduino.sats
| `-- lcd.sats
|-- avr_prelude
| |-- DATS
| | `-- string0.dats
| |-- SATS
| | `-- string0.sats
| |-- kernel_prelude.cats
| `-- kernel_staload.hats
`-- demo
`-- lcd_ats
|-- DATS
| `-- main.dats # <= Start from here.
`-- config.hats

21. main.dats sequence

22. lcd.sats

23. Power of Dependent Type #1
$ pwd
/home/kiwamu/src/arduino-ats/demo/lcd_ats
$ vi DATS/main.dats
$ git diff
diff --git a/demo/lcd_ats/DATS/main.dats b/demo/lcd_ats/DATS/
main.dats
index ab94597..f00eccd 100644
--- a/demo/lcd_ats/DATS/main.dats
+++ b/demo/lcd_ats/DATS/main.dats
@@ -13,7 +13,7 @@ val g_str_message = " ATS is a
statically typed programming lang
implement main0 () = {
fun loop {n:int}{i:nat | i < n}
(lcd: !lcd_t, str: string (n), pos: size_t (i)): void
= {
- val () = if pos + lcd_width <= length str then {
+ val () = if pos + lcd_width <= 1 + length str then {
val () = lcd_setCursor (lcd, 1, 0)
val () = lcd_print (lcd, g_str_atsrun, i2sz 0, length
g_str_atsrun)
val () = lcd_setCursor (lcd, 0, 1)

24. Power of Dependent Type #2
$ make
--snip--
patsopt -o DATS/main_dats.c -d DATS/main.dats
/home/kiwamu/src/arduino-ats/demo/lcd_ats/DATS/main.dats: 958
(line=20, offs=25) -- 958(line=20, offs=25): error(3): unsolved
constraint: C3NSTRprop(main; S2Eapp(S2Ecst(<=); S2Eapp(S2Ecst(+);
S2EVar(1830->S2Evar(i(5501))), S2EVar(1831->S2Eintinf(16))), S2EVar
(1829->S2Evar(n(5500)))))
typechecking has failed: there are some unsolved constraints:
please inspect the above reported error message(s) for information.
☆ ATS2 finds issue at compile time!
☆ Constraint "i + j <= n" is at lcd.sats
☆ main.dats violates the constraint

25. Power of Linear Type #1
$ pwd
/home/kiwamu/src/arduino-ats/demo/lcd_ats
$ vi DATS/main.dats
$ git diff
diff --git a/demo/lcd_ats/DATS/main.dats b/demo/lcd_ats/DATS/
main.dats
index ab94597..4c73340 100644
--- a/demo/lcd_ats/DATS/main.dats
+++ b/demo/lcd_ats/DATS/main.dats
@@ -25,6 +25,7 @@ implement main0 () = {
fun forever {n:int}{i:nat | i < n}
(lcd: !lcd_t, str: string (n), pos: size_t (i)):
void = {
val () = loop (lcd, str, pos)
+ val () = lcd_close lcd
val () = forever (lcd, str, pos)
}
val lcd = lcd_open (8, 13, 9, 4, 5, 6, 7)

26. Power of Linear Type #2
$ make
--snip--
patsopt -o DATS/main_dats.c -d DATS/main.dats
/home/kiwamu/src/arduino-ats/demo/lcd_ats/DATS/main.dats: 1263
(line=29, offs=23) -- 1266(line=29, offs=26): error(3): the linear
dynamic variable [lcd$1182(-1)] is no longer available.
/home/kiwamu/src/arduino-ats/demo/lcd_ats/DATS/main.dats: 1263
(line=29, offs=23) -- 1266(line=29, offs=26): error(3): the
dynamic expression cannot be assigned the type [S2Ecst(lcd_t)].
☆ ATS2 finds issue at compile time!
☆ Linear value "lcd" is consumed
☆ However "lcd" is used by "forever"

27. [5] Japan ATS User Group
http://jats-ug.metasepi.org/

28. Doc: ATSプログラミング入門
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29. Doc: チュートリアル
hhhttttttppp::://////jjjaaatttsss---uuuggg...mmmeeetttaaassseeepppiii...ooorrrggg///dddoooccc///AAATTTSSS222///AAATTTSSS222TTTUUUTTTOOORRRIIIAAALLL///

30. Doc: MLプログラマ向けガイド
https://github.com/jats-ug/translate/blob/master/Web/cs.likai.org/
ats/ml-programmers-guide-to-ats.md

31. Doc: ATS2 wiki
hhhttttttpppsss::://////gggiiittthhhuuubbb...cccooommm///gggiiittthhhwwwxxxiii///AAATTTSSS---PPPooossstttiiiaaatttsss///wwwiiikkkiii

32. Functional IoT
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33. Follow me!
https://twitter.com/jats_ug