スタックマシン

type t =
 | POP
 | PUSHI of int
 | ADD
 | SUB
 | MUL
 | PRINTI
 | RET

let codes = [|
	PUSHI 1;
	PUSHI 2;
	ADD;
	PUSHI 10;
	SUB;
	PUSHI 100;
	MUL;
	PRINTI;
	RET

    

    
]
    
let rec exec stack pc = (
	let code = codes.(pc) in
	let npc = pc + 1 in
	match (codes.(pc), stack) with
	| POP,    x::xs ->              exec           xs  npc
	| PUSHI(i),  xs ->              exec       (i::xs) npc
	| ADD, y::x::xs ->              exec ((x + y)::xs) npc
	| SUB, y::x::xs ->              exec ((x - y)::xs) npc
	| MUL, y::x::xs ->              exec ((x * y)::xs) npc
	| PRINTI, x::xs -> print_int x; print_string "\n";
                                    exec           xs  npc
	| RET,    x::xs -> xs
	| _,         xs -> xs
)

let _ = (exec [] 0)

variantな型と、リストを使ってスタックを表して末尾再帰って感じで、こんな感じで書けました。