brainfxxk.ml

let rec char_at s idx = str_sub s idx (idx + 1) in

let rec program tape =
    let mem = Array.make 30000 0 in
    let tape_size = str_length tape in
    let rec jump_fwd pc stack =
        let op = char_at tape pc in
        if op = "[" then jump_fwd (pc + 1) (stack + 1) else
        if op = "]" then
            if stack = 0 then pc else jump_fwd (pc + 1) (stack - 1)
        else
        jump_fwd (pc + 1) stack
    in
    let rec jump_bkwd pc stack =
        let op = char_at tape pc in
        if op = "[" then
            if stack = 0 then pc else jump_bkwd (pc - 1) (stack - 1)
        else
        if op = "]" then jump_bkwd (pc - 1) (stack + 1) else
        jump_bkwd (pc - 1) stack
    in
    let rec step pc ptr =
        if pc >= tape_size then () else
        let op = char_at tape pc in
        if op = ">" then step (pc + 1) (ptr + 1) else
        if op = "<" then step (pc + 1) (ptr - 1) else
        let pc =
            if op = "+" then
                mem.(ptr) <- (mem.(ptr) + 1);
                pc
            else
            if op = "-" then
                mem.(ptr) <- (mem.(ptr) - 1);
                pc
            else
            if op = "." then
                print_str (from_char_code mem.(ptr));
                pc
            else
            if op = "," then
                mem.(ptr) <- (to_char_code (get_char ()));
                pc
            else
            if op = "[" then
                if mem.(ptr) = 0 then
                    jump_fwd (pc + 1) 0
                else
                    pc
            else
            if op = "]" then
                if mem.(ptr) <> 0 then
                    jump_bkwd (pc - 1) 0
                else
                    pc
            else
            pc
        in
        step (pc + 1) ptr
    in
    step 0 0
in
program "+++++++++[>++++++++>+++++++++++>+++++<<<-]>.>++.+++++++..+++.>-.------------.<++++++++.--------.+++.------.--------.>+."