C2042   Invalid lvalue

     Explanation:  You specified a value on the left side of an
     assignment operator that is not a valid identifier.  Only identifiers
     can be assigned values or references.

     The error could happen if you attempted to use the inline assignment
     operator (:=) when you intended to use the compare operator (==), or it
     may be a more obvious error (e.g., 5 := y + 10).

     Action:  Correct and recompile.