On 04/21/09 11:36, Larry Evans wrote:
On 04/15/09 11:39, Larry Evans wrote: [snip]
The following zip file in the vault's variadic_template directory:
[snip]
replaced. This enabled seeing where the errors were occuring. Also, several MPL_ASSERTS were placed in that file to check where the end iterator was being passed to the iter_fold_if_backward_step template. The *.sizeI.compile files shows where the assertions fail. There's always at least one assertion failure. The number of failures is governed by the size of the input sequence.
AFAICT, the iter_fold_if_backward_step should never be passed the end iterator; hence, there's a bug in iter_fold_if_impl.hpp.
[snip] There's now in the same vault directory, while.cpp. This demonstrates how a while_ template can be used with an explicit stack to avoid the problems of iter_fold_if accessing the end iterator. The exlicit stack is the 3ird parameter to: template < typename Iter , typename State , typename Stack > struct forward_state ; This stack is built up during the 1st while_ instantiation and then that stack is traversed during the 2nd while_ instantiation. IOW, an explicit stack is used to simiulate recursion. I think that's about what iter_fold_if_impl was doing with the forward_stepI, for I=0,4 as well as a recursive call to itself. However, as noted above, it mistakenly assumed forward_stepI::iterator, for i=0,3, was not the end iterator. A nice side effect of this solution is the while_ could be used to solve the {or,and)_problem reported here: http://article.gmane.org/gmane.comp.lib.boost.devel/185908 -regards, Larry