On 08/03/2005 08:51 PM, Jonathan Turkanis wrote:
Larry Evans wrote:
child_i_depth_j allows the traversal of a tree of applications. It's useful for accessing, for example, the i-th superclass of the results of mpl/fold, as demonstrated by the test file:
libs/mpl/test/child_i_depth_j_test.cpp
included in the zip file mentioned in the subject line.
Could this be added to mpl? Is there something I could do to facilitate this addition?
Writing some documentation might help. For instance, what is an application? You
accessing, for example, the i-th superclass of the results of mpl/fold,
For example, I've used fold to calculate the size of both a tuple and variant. In order to access the offset of the j-th element of the tuple, I can use child_i_depth_j. I've also used it to access the j-th acceptor method in a class derived the variant. For a variant of n elements, there are n acceptor methods, one for each element. They are generated also with fold. Given that the value of the variant's tag is a run-time value, I need to create a vector of methods and access the appropriate acceptor method.... Oh it's getting to complicated to explain. I'll just upload it to the vault.
say it's defined in application_parts.hpp, but I don't see any definition there.
The comment under child_i_depth_j.zip in: http://boost-sandbox.sourceforge.net/vault/index.php?&direction=0&order=&directory=cppljevans/mpl says it *uses* application_parts. It's defined in child_i_depth_j.hpp. The only reason I mentioned application_parts was that the last time I proposed application_parts I didn't have a real good application for it. child_i_depth_j is such an application.