Re: [Gretl-users] isscalar (was: functions mshape with variable elements and isscalar)

On Fri, 9 Nov 2012, Sven Schreiber wrote: Maybe I was too glib. But actually, it seems to me that all we really need is isnull() -- though I wouldn't propose at this point that we trash the other is*() functions that are documented and working. When/why do we need, e.g., isstring()? One possible use case is simply that you've defined a bunch a variables and now can't remember their types. But IMO that's kinda silly and not worth supporting in itself. The real use case is for function writers who have made certain arguments optional and want to test whether the caller has supplied anything. Here's a stylized example: <hansl> function void foo (string s[null], scalar *x[null]) if isstring(s) printf "Got a string arg: %s\n", s else printf "s: arg is null\n" endif if isnull(x) printf "x: arg is null\n" else printf "Got a scalar arg: %g\n", x endif end function # invocation with no args foo() scalar p = 4 # invocation with args foo("throgmorton", &p) </hansl> The only occasion on which isscalar() would be truly informative would be as a counterpart to isstring in the context above: to see if the caller passed a pointer to scalar when there was the option of not doing so. And isnull() does that job fine. (Note that if a scalar parameter is not "pointerized" but has a default value, using isscalar would not be informative since it will return 1 regardless of whether the caller supplied a value.) But if I'm missing something, please let me know! Allin