24 Feb
2009
24 Feb
'09
12:06 p.m.
On Friday 20 February 2009, Andrei Pelinescu-Onciul wrote:
[..]
I don't really understand this argument. Leaving performance and
optimizations aside, do you really think is better to guess what the
user might have wanted in ambiguous cases, rather then through an error
and point him to explain more clearly what he wants (e.g. use match()
instead of switch() for strings, or use typed variables)?
I think that its important to not make our config script too much like a "real
programming language", with types and cast and this stuff. There is are
reasons that script languages like python or perl are now widely used instead
of e.g. C, even if their dynamic typed nature moves some error checks into
run time. The benefits (higher expressiveness that leads to more compact
code, fewer bugs because of automatic memory management etc..) outplay the
drawbacks, IMHO.
I just
checked in kamailio, we don't throw an error if one mix strings
and ints in a switch case. We also check for a correct type of an
integer in a mixed expression, e.g. if its a valid int value. I don't
think that we convert them implicitly, as many pseudo-variables hold
internally both a string and a integer value, so mixed expression will
work just as intended in
Sorry, but that's just broken (mixed expressions). With the general approach advocated by some people
here, a small error
when writing the script (e.g. forgetting some "") will be visible only at
runtime (and depending where that error is it could take weeks until
that branch of the config is reached and the error is triggered).
I think this is much worse then having to add a little more "details" to
the script (which BTW wouldn't make it any more difficult then any
common programming language).
Well, many people that uses our script language are not programmers. And even
experienced crypto gurus seems to have difficulties with the complexity that
common languages bring with it [1]. ;-)
I'd rather have to declare even variable types
(e.g. int $a), rather
then debugging strange bugs in a script, because I used a var that
happens to get a string value at runtime.
In brief I much prefer adding to the script if this helps check its
correctness at sr -cf time, rather then trying to be excessively friendly
and leaving a lot of potential script bugs pass-through.
The ability to be able to tell that the script would behave correctly
(as his writer wanted it to) and eliminate ambiguous cases is more
important than trying to keep a very reduced script and guessing what
the writer really wanted.
I've of course nothing general against eleminating abiguous cases, like in the
switch statement. If the user mix strings and int values in the cases, we
really should report an error.
Cheers,
Henning
[1] http://blog.fortify.com/blog/fortify/2009/02/20/SHA-3-Round-1