F# implementation

F#/README.md

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+### DESCRIPTION
+
+PETOOH interpreter written in [F#](http://fsharp.org/).
+
+### USAGE
+
+To compile:
+```
+   ~$ fsc.exe petooh.fs
+```
+To launch:
+```
+   ~$ petooh.exe <PETOOH file name>
+```

F#/petooh.fs

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+// PETOOH interpreter on F#
+// Author: Kirill Smirenko, St. Petersburg State University
+
+module Petooh
+
+open System.IO
+
+let memory_size = 65536
+let val_inc = 1
+let val_dec = 2
+let ptr_inc = 3
+let ptr_dec = 4
+let loop_beg = 5
+let loop_end = 6
+let write = 7
+
+let translate (str : string) =
+  let subs (str : string) i =
+      if str.Length > i then str.Substring i else ""
+  let rec tr str =
+    match str with
+    | "" -> []
+    | str when str.StartsWith "Ko" ->
+      val_inc   :: (tr (subs str 2))
+    | str when str.StartsWith "kO" ->
+      val_dec   :: (tr (subs str 2))
+    | str when str.StartsWith "Kudah" ->
+      ptr_inc   :: (tr (subs str 5))
+    | str when str.StartsWith "kudah" ->
+      ptr_dec   :: (tr (subs str 5))
+    | str when str.StartsWith "Kud" ->
+      loop_beg  :: (tr (subs str 3))
+    | str when str.StartsWith "kud" ->
+      loop_end  :: (tr (subs str 3))
+    | str when str.StartsWith "Kukarek" ->
+      write     :: (tr (subs str 7))
+    | _ -> tr (subs str 1)
+  tr str |> List.toArray
+
+let execute (print : string -> unit) (comms : int []) =
+  let memory = Array.create memory_size 0uy
+  let len = comms.Length
+  let ptr = ref 0
+  let rec findRightBracket i l =
+    if i >= len then
+      i
+    else
+      match comms.[i] with
+      | x when x = loop_end ->
+        if l = 0 then i else findRightBracket (i + 1) (l - 1)
+      | x when x = loop_beg ->
+        findRightBracket (i + 1) (l + 1)
+      | _ -> findRightBracket (i + 1) l
+  let rec exec i br =
+    match i < len with
+    | true ->
+      match comms.[i] with
+      | c when c = val_inc ->
+        memory.[!ptr] <- memory.[!ptr] + 1uy
+        exec (i + 1) br
+      | c when c = val_dec ->
+        memory.[!ptr] <- memory.[!ptr] - 1uy
+        exec (i + 1) br
+      | c when c = ptr_inc ->
+        ptr := (!ptr + 1) % memory_size
+        exec (i + 1) br
+      | c when c = ptr_dec ->
+        ptr := (!ptr + memory_size - 1) % memory_size
+        exec (i + 1) br
+      | c when c = loop_beg ->
+        match br with
+        | (l, r) :: t when l = i ->
+          match compare (memory.[!ptr]) 0uy with
+          | 0 -> exec (r + 1) t
+          | _ -> exec (i + 1) br
+        | _ ->
+          let r = findRightBracket (i + 1) 0
+          match compare (memory.[!ptr]) 0uy with
+          | 0 -> exec (r + 1) br
+          | _ -> exec (i + 1) ((i, r) :: br)
+      | c when c = loop_end ->
+        match br with
+        | (l, _) :: t -> exec l br
+        | _ -> ()
+      | c when c = write ->
+        print ((char memory.[!ptr]).ToString())
+        exec (i + 1) br
+      | _ ->
+        exec (i + 1) br
+    | false -> ()
+  exec 0 []
+
+let interpret (print : string -> unit) (filename : string) =
+  try
+    use streamIn = new StreamReader(filename)
+    streamIn.ReadToEnd () |> translate |> (execute print)
+  with
+  | ex -> printfn "%A" ex.Message
+
+[<EntryPoint>]
+let main argv = 
+  if argv.Length = 1 then
+    interpret (printf "%s") (argv.[0])
+  else
+    printfn "Usage: $ petooh.exe <PETOOH file name>"
+  0