On Feb 9, 10:44 am, l h <lhsoft...@gmail.com> wrote:
I understand the basics of typedefs. I've just never seen
them nested within a class before, particularly since the
class is just a collection of typedefs. So you're saying
that this is using the outer class as a namespace for the
typedefs?
Some people use classes as a scoping mechanism, preferring
them over namespaces. Professor John Lakos (author of Large
Scale C++ Design), encouraged this in the past (and may
still), on the grounds that class scope can't be reopened - if
you've found the class/struct, then you know exactly what's
inside it, whereas namespaces can be put together from many
pieces - making it harder to get an accurate idea of their
content. On the other hand, this very ability means
namespaces can unify a logical interface across the bounds of
multiple "physical" files, which IMHO is more important.
Another aspect is that classes force the use of the scope
(i.e. A::B1 must be used), whereas namespaces can be "used" so
"B1" is sufficient. Again, opinions vary as to whether this
is good or bad. Anyway, don't be thrown by the class wrapping
the typedefs... it's just being used like a namespace as you
say....
I don't think that's a very frequent use today. The most common
configuring some template class. Another possibility would be
all of the typedef's, immediately. This is often done when the
derived class needs a lot of typedef's; e.g. when it's a