[Gretl-devel] some questions on null keyword

Dear all, There are several ways to check whether a list is empty, e.g. eval isnull(varname(somelist) eval somelist=null eval nelem(list) 1) Which way is the most efficient/ recommended ? Also, the behavior of null keyword is different with lists and strings, for example somelist = null  is evaluated but eval somestring = null outputs Data types not conformable for operation 2) Is there a compact text on null keyword? I can imagine the following way to use isnull(): Suppose, I want to write a function which creates new variables with automated names. isnull() could be used for checking duplicated names. 3) What are main uses of isnull() Oleh