BF interpreter

gistfile1.fs

open System
open System.Collections.Generic 

let brainfuck raw = 
    let code = [for c in raw -> c] |> Array.ofList
    let memory = Array.create 1024 0
    let createJumpTable = 
        let mutable stack = new Stack<char*int>()
        let mutable jumpTable = new Map<int,int>([])
        for i = 0 to (code.Length-1) do
            let token = code.[i]
            match token with
            | '[' -> stack.Push(token,i)
            | ']' when stack.Count > 0 && fst (stack.Peek()) = '[' -> 
                let jmp = snd (stack.Pop())
                jumpTable <-jumpTable.Add(i,jmp).Add(jmp,i)
            | ']' -> failwith ("Invalid Program at " + i.ToString())
            | _ -> ()
        jumpTable
    let jump = createJumpTable

    let rec bf pc mp = 
        match code.[pc] with
        | _ when pc >= code.Length-1 -> ()
        | '>' -> bf (pc+1) (mp+1)
        | '<' -> bf (pc+1) (mp-1)
        | '+' -> do memory.[mp] <- (memory.[mp]+1)
                 bf (pc+1) mp
        | '-' -> do memory.[mp] <- (memory.[mp]-1) 
                 bf (pc+1) mp
        | '.' -> do Console.Write(char memory.[mp]) 
                 bf (pc+1) mp
        | ',' -> do memory.[mp] <- Console.Read() 
                 bf (pc+1) mp
        | '[' when memory.[mp] = 0 -> bf jump.[pc] mp
        | ']' when memory.[mp] <> 0 -> bf jump.[pc] mp
        | _ -> bf (pc+1) mp
    bf 0 0
        
let program = "++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>."
brainfuck program