Re: [Gretl-devel] built-in functions and namespace issues
My 2 € cents on this:
On Fri, 23 Nov 2018, Allin Cottrell wrote:
* When a function definition is encountered in a regular hansl
script, we
flag an error if it uses the same name as a built-in function. This has the
implication that scripts that run at time t may fail at time t+k if in the
meantime a built-in function has been added to libgretl, with a name equal to
the name of a function in the script. Maybe this should be revisited at some
point.
I don't think it should; IMO this is a very sane policy, and we should
commit to it indefinitely, for the sake of consistency. The most we can do
is give the user an error message that is as explicit as conspicuous as
possible, so that fixing the script becomes easy.
* Function packages: Up till now the situation has not been very
secure. My
testing indicates there have been no collisions to date, but I guess package
writers and libgretl coders must have been careful and/or lucky -- since
packaged functions have been exempt from namespace checks (other than for
inter-package collisions). If a collision with a built-in function had
occurred, the result would have been that the built-in took priority and the
packaged function was ignored. In today's git that is changed as follows:
(1) We reject public packaged functions that collide with built-ins and post
an error message.
(2) We'll accept private packaged functions that collide with built-ins, and
give the packaged function priority in the context of functions that belong
to the package (only).
I have uneasy feelings about (2), though I couldn't put my finger
precisely on why. I'm imagining a situation when somebody downloads a
package, copies a function from it to a script, and sees it failing or,
worse still, giving different results. Hmmm.
I realise the practical difficulties implied in any alternative to rule
(2), but still I'm not 100% convinced.
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Riccardo (Jack) Lucchetti
Dipartimento di Scienze Economiche e Sociali (DiSES)
Università Politecnica delle Marche
(formerly known as Università di Ancona)
r.lucchetti(a)univpm.it
http://www2.econ.univpm.it/servizi/hpp/lucchetti
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