Re: [Gretl-devel] typeof? (was Re: [Gretl-users] isscalar)

On 11/10/2012 07:51 PM, Allin Cottrell wrote: > > 2) As Sven pointed out, if a function accepts a bundle argument -- in a > context where the content of the bundle is not guaranteed to conform to > a known schema -- the writer may need to determine (a) whether a given > bundle contains an item corresponding to a certain key, and also (b) the > type of the item, if present. ... > > OK, so rather than proliferating is*() functions for all types I > suggested a more general typeof() function, which provoked suggestions > and counter-suggestions from Jack and Sven. I'm now not so keen on that > idea. If I'm right that the only serious use case for such testing is in > unpacking bundles [see footnote], This was just the first thing that I could think of. There may be other use cases for the is*() functions. For example, say somebody has a standalone script where at the top he has some global input, and the script is written to cover all cases. Like: <top of script> matrix temp = I(2) # not commented out; active # scalar temp = 1 # commented out; inactive </top of script> And further down in the script only the appropriate parts of the code are executed: if ismatrix(temp) <do matrix stuff> else <do scalar stuff> endif We may not like that programming style, but should hansl really be changed to make this impossible, which has worked until now?

> [footnote: Jack identified a third case where testing of a variable's > type could be useful, namely in working around bugs relating to the > distinction between scalars and 1x1 matrices. I see that point, but I > don't see it as sufficient reason for a fully general typeof() function > if it's the only use case. When I got to thinking about it, I realized > that implementing a general typeof() -- one that doesn't just accept a > string argument (a putative variable name) -- would actually be quite > tricky.] Well, AFAICS we have discussed checking variable names, not more.