[Gretl-devel] idea for the exists()/nelem() situation with lists in functions

Hi, we repeatedly tried to tackle the problem that a gretl list as a function argument with a null default value is special; exists(mylistarg) will return 1 even when mylistarg was left at the default 'null', for historical reasons. Just now we again had a case on the users list that this situation causes confusion. What about this possible solution: Let's introduce a special variant of exists() using a new optional string arg "listarg" as follows: The call exists(mylistarg, "listarg") would be internally rerouted and equivalent to the expression 'nelem(mylistarg) > 0'. Example: <hansl> function void listex( list L[null]) eval exists(L) eval nelem(L) eval exists(L, "listarg") end function listex() # would print out: # 1 -- for exists(L) # 0 -- for nelem(L) # 0 -- for the new exists(L, "listarg") list LL = foo bar listex(LL) # would print out: # 1 # 2 # 1 # And usage without a function arg: exists(LL, "listarg") # not inside a function, might yield an error # ... but treating this just as exists(LL) is also a possibility </hansl> Thoughts? thanks, sven