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Subject: Re: [boost] [modularization] spirtit -> serialization
From: Peter Dimov (lists_at_[hidden])
Date: 2014-06-15 09:30:20

Andrey Semashev wrote:
> Yes, although I don't really understand what a level means. It surely
> doesn't correspond to the number of dependencies, although there is some
> correlation. When deciding whether to use a library in my library I will
> be looking at its dependencies, not some level index.

If we assume that the purpose of the dependency report is to be informative
(it's a report, after all), the problem is how to take the raw dependency
information (which is basically what header includes what) and to distill it
down to a form that will be most useful to humans.

The module level is that information compressed into a single number.
Modules on level N don't include anything from level N+1 and above.

Obviously, a single (small) number can't hold enough information to describe
the actual dependencies in full. It's merely a good proxy. It's something
you quickly check to see if there's something amiss. Seeing boost::array at
level 8 is enough to make one think. Of course, as with all proxies, if you
make the level your sole focus the actual dependencies may suffer as a
result, but suppose we are smart enough to not do that. :-)

Doing secondary dependencies by module is also a way to compress the full
dependency information into something more manageable, more understandable
and more actionable, if you will. It answers the question "why does my
module depend on Tokenizer" by giving you a module chain, instead of 172
(say) header chains.

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