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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: [math] assert policy
Date Thu, 16 Aug 2012 04:36:44 GMT
Asserts can be handy to inject additional checking into execution inside
private areas of a class during unit tests but it should be assumed that
they are disabled any other time (and the unit test should do real
assertion checking redundantly)

On Wed, Aug 15, 2012 at 9:33 PM, James Ring <sjr@jdns.org> wrote:

> Just a quick observation: at Google the Java practices guide says
> assert == "//". Assertions can be disabled, so you should never rely
> on it to crash if something is seriously wrong and you should never
> rely on side-effects of the assert expression.
>
> On Wed, Aug 15, 2012 at 4:02 PM, Gilles Sadowski
> <gilles@harfang.homelinux.org> wrote:
> > On Wed, Aug 15, 2012 at 10:46:06PM +0200, matic wrote:
> >> Sebb, Gilles and I would like to start a discussion [...]
> >   ^^^^
> >
> > It was not that "Sebb" who commented on MATH-845... ;-)
> >
> >> [...]
> >>
> >> @Gilles: sometimes assertion are a form of comments on steroid ->
> >> they will bark at you if you did not read them, and equally
> >> important: they are unambiguous. When I first write a method, it
> >> usually does not work right away. If it contains asserts, I usually
> >> get a clue of what's wrong, and if I don't, I try to write
> >> additional ones before tracking down the failure in a debug session.
> >> It is way faster, it forces me to understand better what I am coding
> >> (when I just follow a algorithm described in a paper, the typical
> >> situation for CM stuff) and the best of all: it will help anyone who
> >> later modify the code.
> >> -> in short, I see assertions as an invaluable tool to help
> >> developers, not just something to check input parameters in private
> >> methods. For this reason, I would support the following policy:
> >> 1. Use asserts as much as you like, but they are by no mean a
> >> substitute to runtime checks (code that throws "MathInternalError")
> >> for input parameters of public methods.
> >> 2. Asserts must be enabled in all unit tests
> >
> > I don't deny that assertions can help you while developing, but the
> > algorithms in the CM library should not be construed as a "work in
> > progress". To be sure, quite a few areas definitely need all kinds of
> > improvements, but what I mean is that when something is checked in, it
> > should be working as expected (bugs notwithstanding) by the developer.
> That
> > means: "assert" statements will not be triggered. Unit tests should be
> > provided to ensure that everything (ideally) behaves as expected.
> >
> > I understand that you did not mean to replace runtime check with
> assertions
> > but I'm a little afraid that "assert" will be considered enough (or
> better
> > than comments), such that the amount of comments will be reduced (while
> the
> > opposite should happen).
> > Moreover, "assert" generally checks "obvious" mistakes, which will happen
> > during development but are much less likely to occur when the finished
> code
> > is being called (I think). Once you start sprinkling "assert" statements
> in
> > a library like CM, it can quickly become littered with hundreds of them
> (in
> > fact there would probably be more "assert" than there are precondition
> > checks). I wondered how more readable that will make the code and for
> what
> > added value.
> > I understand that the readability would suffer (and even more) by
> > introducing logging statements all over the place, but at least that
> would
> > provide the benefit that one could be able to trace a bug to its root
> cause.
> > [I'm saying this because I recently wished I had logging inside a CM
> > alogrithm, while "assert" wouldn't have helped.]
> >
> >
> > Best regards,
> > Gilles
> >
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> >
>
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