pub fn add( left : usize, right : usize ) -> usize
{
  left + right
}

pub fn sub( left : usize, right : usize ) -> usize
{
  left - right
}

#[ cfg( test ) ]
mod tests
{
  use super::*;

  #[ test ]
  fn it_works()
  {
    let result = add( 2, 2 );
    assert_eq!( result, 4 );
  }
}