> Sami>  +		      struct value *value = value_x_unop (arg2, op, noside);
> Sami>  +		      if (value)
> Sami>  +			arg2 = value;
>
> This seems strange.  When can the result here be NULL?  And what does
> that mean?  It seems like this either ought to be impossible, or it
> should be an error of some kind.
>

Yes this is incorrect. value_x_unop never returns null. If the operator 
is not found it throws an error. I added a try catch statement and tests 
for the failing case.

New patch attached.