caml-urm
A OCaml module for manipulating unlimited register machines
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open Array open Genlex type instruction = | T of int * int | Z of int | S of int | P of int | J of int * int * int type t = { instruction_pointer : int; registers : int -> int; } type machine = t let of_registers f = { instruction_pointer = 0; registers = f } let of_list xs = let f acc (reg_n, reg_val) = fun n -> if n = reg_n then reg_val else acc n in xs |> List.fold_left f (fun _ -> 0) |> of_registers let zeros = of_registers (fun _ -> 0) let register m = m.registers (** Executes the next instruction. Returns [Some _] is the instruction pointer points to a valid adress and [None] otherwise. *) let step (program : instruction array) (m : machine) : machine option = if m.instruction_pointer >= length program then None else let updated = match program.(m.instruction_pointer) with | T (r1, r2) -> { registers = (fun n -> if n == r2 then m.registers r1 else m.registers n); instruction_pointer = m.instruction_pointer + 1; } | Z r -> { registers = (fun n -> if n == r then 0 else m.registers n); instruction_pointer = m.instruction_pointer + 1; } | S r -> { registers = (fun n -> if n == r then 1 + (m.registers n) else m.registers n); instruction_pointer = m.instruction_pointer + 1; } | P r -> { registers = (fun n -> if n == r then (m.registers n) - 1 else m.registers n); instruction_pointer = m.instruction_pointer + 1; } | J (r1, r2, i) when m.registers r1 == m.registers r2 -> (* [i - 1] is used so that the instruction count starts at 1 instead of 0 *) if i > 0 then { m with instruction_pointer = i - 1 } else let e = Printf.sprintf "invalid jump address: J(%d, %d, %d)" r1 r2 i in raise (Invalid_argument e) | J _ -> { m with instruction_pointer = m.instruction_pointer + 1 } in Some updated let rec exec program m = match step program m with | None -> { m with instruction_pointer = 0 } | Some n -> exec program n let nexec max program m = if max <= 0 then raise (Invalid_argument "the number of clock-cycles must be positive ") else let rec exec_safe_tail m clock_cycles = if clock_cycles <= max then match step program m with | None -> Some { m with instruction_pointer = 0 } | Some n -> exec_safe_tail n (clock_cycles + 1) else None in exec_safe_tail m 0 (********************************** Parsing **********************************) exception Syntax_error of string (** A simple lexer for instructions *) let lex = make_lexer ["T"; "Z"; "S"; "P"; "J"; "("; ")"; ","] (** Parse a single instruction *) let parse_instruction (i : token list) : instruction = match i with | [ Kwd "T"; Kwd "("; Int r1; Kwd ","; Int r2; Kwd ")" ] -> T (r1, r2) | [ Kwd "Z"; Kwd "("; Int r; Kwd ")" ] -> Z r | [ Kwd "S"; Kwd "("; Int r; Kwd ")" ] -> S r | [ Kwd "P"; Kwd "("; Int r; Kwd ")" ] -> P r | [ Kwd "J"; Kwd "("; Int r1; Kwd ","; Int r2; Kwd ","; Int i; Kwd ")" ] when i > 0 -> J (r1, r2, i) | [ Kwd "J"; Kwd "("; Int _; Kwd ","; Int _; Kwd ","; Int i; Kwd ")" ] -> raise (Syntax_error (Printf.sprintf "invalid jump address: %d" i)) | _ -> raise (Syntax_error "invalid syntax") let parse (s : string) : instruction array = let f s = let s = String.trim s in if s = "" then None else s |> Stream.of_string |> lex |> Stream.npeek 8 |> parse_instruction |> Option.some in s |> String.split_on_char '\n' |> List.filter_map f |> Array.of_list