use std::io;
use std::io::Read;
use command::Command;


type Cell = u8;

pub struct VM {
    cells: [Cell; 30_000],
    data_pointer: usize,
}


impl VM {
    pub fn new() -> VM {
        VM { cells: [0; 30_000], data_pointer: 0 }
    }


    pub fn output(&self) {
        print!("{}", self.cells[self.data_pointer]);
    }


    pub fn input(&self) {
        let mut buffer = [0; 1];
        let mut stdin = io::stdin();
        stdin.read_exact(&mut buffer).unwrap();
    }


    pub fn increment(&mut self) {
        self.cells[self.data_pointer] = self.cells[self.data_pointer] + 1;
    }


    pub fn decrement(&mut self) {
        self.cells[self.data_pointer] = self.cells[self.data_pointer] - 1;
    }


    pub fn right_shift(&mut self) {
        self.data_pointer = self.data_pointer + 1;
    }


    pub fn left_shift(&mut self) {
        self.data_pointer = self.data_pointer - 1;
    }


    pub fn apply(&mut self, command: Command) {
        match command {
            Command::Output => self.output(),
            Command::Input => self.input(),
            Command::Increment => self.increment(),
            Command::Decrement => self.decrement(),
            Command::RightShift => self.right_shift(),
            Command::LeftShift => self.left_shift(),
        }
    }
}

use std::io;
use std::io::Read;


type Cell = u8;

pub struct VM {
    cells: [Cell; 30_000],
    data_pointer: usize,
}


impl VM {
    pub fn new() -> VM {
        VM { cells: [0; 30_000], data_pointer: 0 }
    }


    pub fn output(&self) {
        print!("{}", self.cells[self.data_pointer]);
    }


    pub fn input(&self) {
        let mut buffer = [0; 1];
        let mut stdin = io::stdin();
        stdin.read_exact(&mut buffer).unwrap();
    }


    pub fn increment(&mut self) {
        self.cells[self.data_pointer] = self.cells[self.data_pointer] + 1;
    }


    pub fn decrement(&mut self) {
        self.cells[self.data_pointer] = self.cells[self.data_pointer] - 1;
    }


    pub fn right_shift(&mut self) {
        self.data_pointer = self.data_pointer + 1;
    }


    pub fn left_shift(&mut self) {
        self.data_pointer = self.data_pointer - 1;
    }
}

--- 
+++ 
@@ -1,5 +1,6 @@
 use std::io;
 use std::io::Read;
+use command::Command;
 
 
 type Cell = u8;
@@ -46,4 +47,16 @@
     pub fn left_shift(&mut self) {
         self.data_pointer = self.data_pointer - 1;
     }
+
+
+    pub fn apply(&mut self, command: Command) {
+        match command {
+            Command::Output => self.output(),
+            Command::Input => self.input(),
+            Command::Increment => self.increment(),
+            Command::Decrement => self.decrement(),
+            Command::RightShift => self.right_shift(),
+            Command::LeftShift => self.left_shift(),
+        }
+    }
 }
Add apply function to VM
