calc.ml

calc.ml

type c =
  | Int of int
  | Add
  | Sub
  | Load of string
  | Save of string
  | Ret

let rec lookup e v =
  match e with
  | [] -> assert false
  | (a,r)::e when  a = v -> r
  | _::e -> lookup e v

let rec sec = function
  | (a::s,e,Ret::c) -> a
  | (s,e,Int i::c) -> sec(i::s, e, c)
  | (a::b::s,e,Add::c) -> sec(a+b::s,e,c)
  | (a::b::s,e,Sub::c) -> sec(a-b::s,e,c)
  | (a::s,e,Save(v)::c) -> sec(s,(v,a)::e,c)
  | (s,e,Load(v)::c) -> sec(lookup e v::s,e,c)
  | _ -> assert false

let _ =
  Printf.printf "%d\n" (sec([],[],[Int 1;Int 2; Add; Save("a"); Int 10; Int 20; Sub; Save("b"); Load("a"); Load("b"); Add; Ret]))
  
type e =
  | EInt of int
  | EVar of string
  | EAdd of e * e
  | ESub of e * e
  | ELet of string * e * e

let rec comp = function
  | EInt i -> [Int i]
  | EVar s -> [Load s]
  | EAdd(a,b) -> comp b @ comp a @ [Add]
  | ESub(a,b) -> comp b @ comp a @ [Sub]
  | ELet(s,a,b) -> comp a @ Save s :: comp b

let compile e = comp e @ [Ret]

let _ =
  Printf.printf "%d\n" (sec([],[], compile(
    ELet("a", EAdd(EInt 1, EInt 2),
    ELet("b", ESub(EInt 20,EInt 10),
    EAdd(EVar("a"),EVar("b")))) )))
  

interp.ml

let rec lookup e v =
  match e with
  | [] -> assert false
  | (a,r)::e when  a = v -> r
  | _::e -> lookup e v

type e =
  | EInt of int
  | EVar of string
  | EAdd of e * e
  | ESub of e * e
  | ELet of string * e * e

let rec eval env = function
  | EInt i -> i
  | EVar s -> lookup env s
  | EAdd(a,b) -> eval env a + eval env b
  | ESub(a,b) -> eval env a - eval env b
  | ELet(s,a,b) -> eval ((s, eval env a)::env) b

let _ =
  Printf.printf "%d\n" (eval [] (
    ELet("a", EAdd(EInt 1, EInt 2),
    ELet("b", ESub(EInt 20,EInt 10),
    EAdd(EVar("a"),EVar("b")))) ))