[cpp-netlib-devel] Compile-Time Reduction

[Dean M. B. <mik...@gm...>]

In the same line as my previous message, I have made a simple step
that also greatly reduces compile times now with the tag dispatch
mechanism. With my recent change: http://goo.gl/4A5I I was able to
reduce the compile time of the tests with just using a simple
technique for compile-time "type erasure" to avoid the excessive
template instantiations throughout the library with regards to tags.
In the commit message I explain what I did and how it affects compile
times immensely. I'm copying the commit message here for posterity and
feedback:

--8<---

Compile-time Reduction Techniques

This commit hilights the effect of hiding the MPL details into the
base class instead of a typedef. Instead of just a typedef, use
Boost.MPL metafunctions as base classes. i.e. instead of:

  typedef typename mpl::inherit_linearly<...>::type tag_name;

Do this instead:

  struct tag_name : mpl::inherit_linearly<...>::type {};

This then makes the tag back into an opaque type that the
compiler doesn't have to keep instantiating over and over again
in the cases where the tag is used.

Also because all the metafunctions deal with opaque tags and whether
they inherit from specific root/base tags, then the compile times are
greatly reduced. You can call this type erasure at compile-time using
OOP facilities.

--8<---

Let me know if this helps, if anybody can measure the difference
between 0.7 and the latest in 0.8-devel, that would greatly be
appreciated as well. :)

Have a good one guys!

-- 
Dean Michael Berris
deanberris.com