How to Implement a CPU Emulator in Scheme

hBp://mcpc.arnip.org/
#csmeiji

How
to
Implement

a
CPU
Emulator
in
Scheme
Representa9ve
of
MCPC

Kazuhiro
Hishinuma

MCPC:
a
Compe99ve
Programming
Circle
1

The Trigger
to
Implement
a
CPU
Emulator

MCPC:
a
Compe99ve
Programming
Circle
2

MCPC:
a
Compe99ve
Programming
Circle
3

MCPC:
a
Compe99ve
Programming
Circle
4

MCPC:
a
Compe99ve
Programming
Circle
5

MCPC:
a
Compe99ve
Programming
Circle
6

(
◠‿◠
)☛

Make
It
Yourself
MCPC:
a
Compe99ve
Programming
Circle
7

▂▅▇█▓▒░('ω')░▒▓█▇▅▂

▂▅▇█▓▒░('ω')░▒▓█▇▅▂

▂▅▇█▓▒░('ω')░▒▓█▇▅▂

MCPC:
a
Compe99ve
Programming
Circle
8

The Reason
to
Implement
in
Scheme

MCPC:
a
Compe99ve
Programming
Circle
9

In
Scheme,
You
can
…

Get
Current
Con9nua9on

And

Return
Mul9ple
Values

MCPC:
a
Compe99ve
Programming
Circle
10

Con9nua9on...?
/*
Pseudo-‐Code
*/

func9on
f
(
x
)
{

res
=
x
+
1;
Con9nua9on
:=

A
Func9on-‐Like
Object

To
Return
Value!!!

return
(
res
);

};

MCPC:
a
Compe99ve
Programming
Circle
11

What’s
the
Diﬀerence

Between
Func9on

And
Con9nua9on??

MCPC:
a
Compe99ve
Programming
Circle
12

(
◠‿◠
)☛In
Func9on

CALL

PROGRAM
FUNCTION
RETURN

MCPC:
a
Compe99ve
Programming
Circle
13

(
◠‿◠
)☛In
Con9nua9on

CALL
CONTINU-‐

PROGRAM
ATION

MCPC:
a
Compe99ve
Programming
Circle
14

(
◠‿◠
)☛

A
Con9nua9on
is

Like
A
Func9on,

But
It
Won’t
Return.
MCPC:
a
Compe99ve
Programming
Circle
15

o。(˘⊖˘
)

A
Con9nua9on
is

Like
A
Func9on…?

MCPC:
a
Compe99ve
Programming
Circle
16

┗(☋｀ )┓三

return
(
a,
b,
c
);

MCPC:
a
Compe99ve
Programming
Circle
17

f
(
x
)
returns
y

x
f
(
x
)
y
MCPC:
a
Compe99ve
Programming
Circle
18

f
(
x
)
returns
(
a,
b,
c
)

x
a
f
(
x
)
b
c
MCPC:
a
Compe99ve
Programming
Circle
19

ヾ(*＞ヮ＜)ﾉ

A
Func9on
Returns

Mul9ple
Values!!

MCPC:
a
Compe99ve
Programming
Circle
20

Mul9ple
Values
Func9on

x
a
b
f
(
x
)
c

MCPC:
a
Compe99ve
Programming
Circle
21

Composing
Func9ons

x

f
(
x
)
g
(
a,
b,
c
)
d
e
MCPC:
a
Compe99ve
Programming
Circle
22

Composing
Func9ons…?
3

fetch
generator

2

MCPC:
a
Compe99ve
Programming
Circle
23

This
is
a
Hardware
Diagram!!
clk_gen

MUX
0
dec7seg
counter

dec7seg
decoder

MCPC:
a
Compe99ve
Programming
Circle
24

＿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
25

The Way
to
Implement
a
CPU
Emulator

MCPC:
a
Compe99ve
Programming
Circle
26

(
◠‿◠
)☛Read
it!

MCPC:
a
Compe99ve
Programming
Circle
27

(
◠‿◠
)☛980
yen
(tax
in)
日
経

年

月
号

MCPC:
a
Compe99ve
Programming
Circle
28

(
◠‿◠
)☛Implement
It!!

gr
mem
run

fr
fetch

pc
<machine>
MCPC:
a
Compe99ve
Programming
Circle
29

(ฅ`･ω･´)っ=

There
is
One
Problem.

MCPC:
a
Compe99ve
Programming
Circle
30

State
Transi9on
on
Hardware
is
…

DESTRUCTIVE!!
MCPC:
a
Compe99ve
Programming
Circle
31

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
32

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
33

p
(`･ω･´q)

It’s
Solved.

MCPC:
a
Compe99ve
Programming
Circle
34

The Result
of
Implement
in
Scheme

MCPC:
a
Compe99ve
Programming
Circle
35

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

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

hBp://mcpc.arnip.org/

Thanks
for

YOUR
listening!

MCPC:
a
Compe99ve
Programming
Circle
38

How to Implement a CPU Emulator in Scheme

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