Why do i get keep on getting variable not introduced in Oz programming?

Question

I keep on getting an error, variable MainMirror Not introduced. How do I fix this?

fun {MainMirror Int}

    local Mirror in
        fun {Mirror Int Acc}
       if Int == 0 then Acc
       else
          Acc + {Mirror (Int div 10) (Acc mod 10)} end
        end
        {Mirror Int 0}
    end
end
{Browse {MainMirror 1234}}

Answer 1

You did not declare your variable MainMirror. In fact a function is a variable in OZ. You can declare MainMirror using 'declare' operator or 'local'.

declare
fun {MainMirror Int}

local Mirror in
    fun {Mirror Int Acc}
   if Int == 0 then Acc
   else
      Acc + {Mirror (Int div 10) (Acc mod 10)} end
    end
    {Mirror Int 0}
end
end
{Browse {MainMirror 1234}}