struct AST_Node {
      #ifdef DEBUG_MODE
      string expression;
      #endif
      jdip::token_t token; ///< A copy of the token which was used to create this node.
    };
    /// Child of AST_Node for unary operators.
    struct AST_Node_Unary: AST_Node {
      AST_Node *right; ///< The stuff we're operating on.
    };
    /// Child of AST_Node for binary operators.
    struct AST_Node_Binary: AST_Node {
      AST_Node *left, ///< The left-hand side of the expression.
               *right; ///< The right-hand side of the expression.
    };
    /// Child of AST_Node for the ternary operator.
    struct AST_Node_Ternary: AST_Node {
      AST_Node *exp, ///< The expression before the question marks.
               *left, ///< The left-hand (true) result.
               *right; ///< The right-hand (false) result.
    };