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Implemented control constructs

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Dmitry Boulytchev 2018-03-20 20:30:58 +03:00
commit a60a491e73
23 changed files with 487 additions and 9 deletions
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31
src/Language.ml
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@ -113,7 +113,8 @@ module Stmt =
(* composition *) | Seq of t * t
(* empty statement *) | Skip
(* conditional *) | If of Expr.t * t * t
(* loop *) | While of Expr.t * t with show
(* loop with a pre-condition *) | While of Expr.t * t
(* loop with a post-condition *) | Repeat of t * Expr.t with show
(* The type of configuration: a state, an input stream, an output stream *)
type config = Expr.state * int list * int list
@ -133,6 +134,7 @@ module Stmt =
| Skip -> conf
| If (e, s1, s2) -> eval conf (if Expr.eval st e <> 0 then s1 else s2)
| While (e, s) -> if Expr.eval st e = 0 then conf else eval (eval conf s) stmt
| Repeat (s, e) -> let (st, _, _) as conf' = eval conf s in if Expr.eval st e = 0 then eval conf' stmt else conf'
(* Statement parser *)
ostap (
@ -140,12 +142,27 @@ module Stmt =
s:stmt ";" ss:parse {Seq (s, ss)}
| stmt;
stmt:
%"read" "(" x:IDENT ")" {Read x}
| %"write" "(" e:!(Expr.parse) ")" {Write e}
| %"skip" {Skip}
| %"if" e:!(Expr.parse) %"then" s1:parse %"else" s2:parse %"fi" {If (e, s1, s2)}
| %"while" e:!(Expr.parse) %"do" s:parse %"od" {While (e, s)}
| x:IDENT ":=" e:!(Expr.parse) {Assign (x, e)}
%"read" "(" x:IDENT ")" {Read x}
| %"write" "(" e:!(Expr.parse) ")" {Write e}
| %"skip" {Skip}
| %"if" e:!(Expr.parse)
%"then" the:parse
elif:(%"elif" !(Expr.parse) %"then" parse)*
els:(%"else" parse)?
%"fi" {
If (e, the,
List.fold_right
(fun (e, t) elif -> If (e, t, elif))
elif
(match els with None -> Skip | Some s -> s)
)
}
| %"while" e:!(Expr.parse) %"do" s:parse %"od"{While (e, s)}
| %"for" i:parse "," c:!(Expr.parse) "," s:parse %"do" b:parse %"od" {
Seq (i, While (c, Seq (b, s)))
}
| %"repeat" s:parse %"until" e:!(Expr.parse) {Repeat (s, e)}
| x:IDENT ":=" e:!(Expr.parse) {Assign (x, e)}
)
end