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|
open Static
let pow a n =
let rec g p x = function
| 0 -> x
| i ->
g (p * p) (if i mod 2 = 1 then p * x else x) (i/2)
in
g a 1 n
;;
let fun_of_op op = match op with
| SAdd -> (+) | SMinus -> (-)
| SMult -> (fun i1 i2 -> i1 * i2)
| SDiv -> (/)
| SPower -> pow
| _ -> assert false
let fun_of_comp_op op = match op with
| SEqual -> (=) | SLeq -> (<=) | SLess -> (<)
| _ -> assert false
let rec simplify env se = match se.se_desc with
| SInt _ | SBool _ -> se
| SVar n ->
(try
let se = NameEnv.find n env in
simplify env se
with
| Not_found -> se)
| SBinOp(op, se1, se2) ->
let se1 = simplify env se1 in
let se2 = simplify env se2 in
let desc =
match op, se1.se_desc, se2.se_desc with
| (SAdd | SMinus | SDiv | SMult | SPower), SInt i1, SInt i2 ->
let f = fun_of_op op in
SInt (f i1 i2)
| (SEqual | SLess | SLeq | SGreater | SGeq), SInt i1, SInt i2 ->
let f = fun_of_comp_op op in
SBool (f i1 i2)
| _, _, _ -> SBinOp(op, se1, se2)
in
{ se with se_desc = desc }
| SIf(c, se1, se2) ->
let c = simplify env c in
let se1 = simplify env se1 in
let se2 = simplify env se2 in
(match c.se_desc, se1.se_desc, se2.se_desc with
| SBool true, _, _ -> se1
| SBool false, _, _ -> se2
| _, sed1, sed2 when sed1 = sed2 -> { se with se_desc = sed1 }
| _, _, _ -> { se with se_desc = SIf(c, se1, se2) })
let rec subst env se = match se.se_desc with
| SInt _ | SBool _ -> se
| SVar n ->
(try
NameEnv.find n env
with
| Not_found -> se)
| SBinOp(op, se1, se2) ->
{ se with se_desc = SBinOp(op, subst env se1, subst env se2) }
| SIf(c, se1, se2) ->
{ se with se_desc = SIf(subst env c, subst env se1, subst env se2) }
exception Unsatisfiable of static_exp
let check_true env cl =
let check_one c =
let res = simplify env c in
match res.se_desc with
| SBool true -> ()
| _ -> raise (Unsatisfiable c)
in
List.iter check_one cl
|
