This document discusses implementing a CPU emulator in Scheme. It explains that Scheme is well-suited for this because it allows getting the current continuation and returning multiple values. State transitions can be expressed as tail calls, allowing pure state transitions. The document provides code samples and diagrams demonstrating how to represent hardware components like clocks and memory in Scheme. It concludes that Scheme is a hardware description language and implementing a CPU emulator in it is an interesting way to learn about programming with continuations.

1. hBp://mcpc.arnip.org/
#csmeiji
How
to
Implement
a
CPU
Emulator
in
Scheme
Representa9ve
of
MCPC
Kazuhiro
Hishinuma
MCPC:
a
Compe99ve
Programming
Circle
1

2. The Trigger
to
Implement
a
CPU
Emulator
MCPC:
a
Compe99ve
Programming
Circle
2

3. MCPC:
a
Compe99ve
Programming
Circle
3

4. MCPC:
a
Compe99ve
Programming
Circle
4

5. MCPC:
a
Compe99ve
Programming
Circle
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6. MCPC:
a
Compe99ve
Programming
Circle
6

7. (
◠‿◠
)☛
Make
It
Yourself
MCPC:
a
Compe99ve
Programming
Circle
7

8. ▂▅▇█▓▒░('ω')░▒▓█▇▅▂
▂▅▇█▓▒░('ω')░▒▓█▇▅▂
▂▅▇█▓▒░('ω')░▒▓█▇▅▂
MCPC:
a
Compe99ve
Programming
Circle
8

9. The Reason
to
Implement
in
Scheme
MCPC:
a
Compe99ve
Programming
Circle
9

10. In
Scheme,
You
can
…
Get
Current
Con9nua9on
And
Return
Mul9ple
Values
MCPC:
a
Compe99ve
Programming
Circle
10

11. Con9nua9on...?
/*
Pseudo-­‐Code
*/
func9on
f
(
x
)
{
res
=
x
+
1;
Con9nua9on
:=
A
Func9on-­‐Like
Object
To
Return
Value!!!
return
(
res
);
};
MCPC:
a
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11

12. What’s
the
Difference
Between
Func9on
And
Con9nua9on??
MCPC:
a
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Programming
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13. (
◠‿◠
)☛In
Func9on
CALL
PROGRAM
FUNCTION
RETURN
MCPC:
a
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Programming
Circle
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14. (
◠‿◠
)☛In
Con9nua9on
CALL
CONTINU-­‐
PROGRAM
ATION
MCPC:
a
Compe99ve
Programming
Circle
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15. (
◠‿◠
)☛
A
Con9nua9on
is
Like
A
Func9on,
But
It
Won’t
Return.
MCPC:
a
Compe99ve
Programming
Circle
15

16. o。(˘⊖˘
)
A
Con9nua9on
is
Like
A
Func9on…?
MCPC:
a
Compe99ve
Programming
Circle
16

17. ┗(☋｀ )┓三
return
(
a,
b,
c
);
MCPC:
a
Compe99ve
Programming
Circle
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18. f
(
x
)
returns
y
x
f
(
x
)
y
MCPC:
a
Compe99ve
Programming
Circle
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19. f
(
x
)
returns
(
a,
b,
c
)
x
a
f
(
x
)
b
c
MCPC:
a
Compe99ve
Programming
Circle
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20. ヾ(*＞ヮ＜)ﾉ
A
Func9on
Returns
Mul9ple
Values!!
MCPC:
a
Compe99ve
Programming
Circle
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21. Mul9ple
Values
Func9on
x
a
b
f
(
x
)
c
MCPC:
a
Compe99ve
Programming
Circle
21

22. Composing
Func9ons
x
f
(
x
)
g
(
a,
b,
c
)
d
e
MCPC:
a
Compe99ve
Programming
Circle
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23. Composing
Func9ons…?
3
fetch
generator
2
MCPC:
a
Compe99ve
Programming
Circle
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24. This
is
a
Hardware
Diagram!!
clk_gen
MUX
0
dec7seg
counter
dec7seg
decoder
MCPC:
a
Compe99ve
Programming
Circle
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25. ＿人人人人人人人人＿
＞ Scheme
is
a
HDL!! ＜
￣^Y^Y^Y^Y^Y^Y^Y^Y^￣
MCPC:
a
Compe99ve
Programming
Circle
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26. The Way
to
Implement
a
CPU
Emulator
MCPC:
a
Compe99ve
Programming
Circle
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27. (
◠‿◠
)☛Read
it!
MCPC:
a
Compe99ve
Programming
Circle
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28. (
◠‿◠
)☛980
yen
(tax
in)
日
経
年
月
号
MCPC:
a
Compe99ve
Programming
Circle
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29. (
◠‿◠
)☛Implement
It!!
gr
mem
run
fr
fetch
pc
<machine>
MCPC:
a
Compe99ve
Programming
Circle
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30. (ฅ`･ω･´)っ=
There
is
One
Problem.
MCPC:
a
Compe99ve
Programming
Circle
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31. State
Transi9on
on
Hardware
is
…
DESTRUCTIVE!!
MCPC:
a
Compe99ve
Programming
Circle
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32. Destruc9ve
State
Transi9on
/*
Pseudo-­‐Code,
Given
s:
Current
State
*/
S1:
/*
Procedure
of
State
S1
*/
s
=
/*
S1-­‐>S2
*/(
s
);
goto
S2;
S2:
/*
Procedure
of
State
S2
*/
/*
…
*/
MCPC:
a
Compe99ve
Programming
Circle
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33. Pure
State
Transi9on
/*
Pseudo-­‐Code,
Given
s:
Current
State
*/
func9on
S1
(
s
)
{
/*
Procedure
of
State
S1
*/
return
S2
(
/*
S1-­‐>S2
*/(
s
)
);
}
func9on
S2
(
s
)
{
/*
Procedure
of
State
S2
...
Tail
Call
MCPC:
a
Compe99ve
Programming
Circle
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34. p
(`･ω･´q)
It’s
Solved.
MCPC:
a
Compe99ve
Programming
Circle
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35. The Result
of
Implement
in
Scheme
MCPC:
a
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Programming
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36. hBps://gist.github.com/kazh98/5117299 解説:
hBp://qiita.com/items/b667dc18e769c4bf857e
hBps://gist.github.com/kazh98/5213280 解説:
このスライド
(
◠‿◠
)☛Demonstra9on
MCPC:
a
Compe99ve
Programming
Circle
36

37. Conclusion
• Scheme
is
a
Hardware
Descrip9on
Language.
• State
Transi9on
can
be
Expressed
as
Tail
Call.
• To
Implement
CPU
Emulator
is
interes9ng.
Let
us
Be
a
Schemer!!
MCPC:
a
Compe99ve
Programming
Circle
37

38. hBp://mcpc.arnip.org/
Thanks
for
YOUR
listening!
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