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Subject: Re: [boost] [assert] static_assert envy
From: Robert Kawulak (robert.kawulak_at_[hidden])
Date: 2011-01-18 19:55:10

> From: Patrick Horgan
> > I can't agree. The macros reduce complexity by simplifying the boolean expressions and by being more
> descriptive, thus better
> > expressing the author's intention.
> You have a certain logic, but what I meant was that BOOST_FAIL_MSG could
> be built in terms of BOOST_ASSERT. It adds another layer of indirection
> on top of it.

Yes, it does. It seems like you're talking more about complexity of making the tool, while I talk about complexity of using the
tool. For me, seeing and understanding a line with BOOST_ASSERT_IF_MSG would be way easier than the equivalent BOOST_ASSERT with the
boolean expression. Similarly, BOOST_FAIL_MSG("msg") would be telling me what's happening at a glance while BOOST_ASSERT(!"msg") or
BOOST_ASSERT_MSG(false, "msg") would require a little bit more time to parse.

> > And one could argue that C++ casts may add complexity as well, e.g. when you have
> >
> > const_cast<derived*>(dynamic_cast<const derived*>(const_base_ptr))
> >
> > instead of
> >
> > (derived *) const_base_ptr
> The first uses simpler parts though, to accomplish what the more complex
> old style cast could do in one fell swoop. You've made my point, the
> old style cast is much more complex containing much meaning that leads
> to confusion and error often as not.

Now you've made my point. ;-) Using BOOST_ASSERT (C cast) to express all the kinds of assertions (type conversions) is more complex
in the same sense as it may lead to confusion and errors. This is why I'd like to have these macros (C++ casts) - to have simpler,
more specialised code-building blocks. It doesn't matter whether the simpler is implemented in terms of the more complex or the
other way round - the effect is what counts.

> BOOST_FAIL_MSG would be like the old style
> cast in that is subsumes more intent without exposing it to you.

I think exactly the opposite: BOOST_FAIL_MSG functionality is a subset of BOOST_ASSERT functionality, just like any C++ cast is a
subset of the C cast. By using the less general tool you communicate your intention more precisely.

Best regards,

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