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|
(******************************************************************************
* Defines a generic parser class.
******************************************************************************)
open Vec
exception ParseError of string
type token = string
type state = { i : int; tokens : token vec }
class parser (tokens : token vec) =
object (self)
val mutable tokens = tokens
val mutable i = ref 0
method advance = i := !i + 1
method prev : token option = Vec.get (!i - 1) tokens
method curr : token option = Vec.get !i tokens
method next : token option = Vec.get (!i + 1) tokens
method consume : token option =
match self#curr with
| None -> None
| Some x as res ->
self#advance;
res
method expect (x : token) =
match self#curr with
| Some y when x = y -> self#advance
| _ -> raise (ParseError (Printf.sprintf "Expected %s" x))
method matches (x : token) : bool =
match self#curr with
| None -> false
| Some y ->
if x = y then
begin
self#advance;
true
end
else false
method exhausted : bool = !i >= Vec.length tokens
method state : state = { i = !i; tokens }
end
|
