Use EBO to minimize wasted storage space if the predicate is an empty class.
Disable default constructing non-class predicates using SFINAE instead
of a static_assert. This will help type traits like is_constructible,
when applied to the iterator type.
The new eval_if_default helper replaces both ia_dflt_help and
ia_eval_if_default helpers. Additionally, added a new if_default
helper, which expands to the type or the default parameter directly.
The new helpers are placed in separate headers which can be used
without the iterator_adaptor template.
The new min_category is similar to minimum_category but accepts variable
number of iterator categories on input instead of just two, and also does
not depend on Boost.MPL for lambda placeholders. The existing minimum_category
trait has been reimplemented in terms of min_category and deprecated.
We don't yet emit deprecation warnings as there is still code that uses
the old trait which we first need to update. Eventually, minimum_category
will emit warnings and will be removed.
Performance improvement: Add move semantics to by-value parameters (iterator and predicate), to eliminate the cost of copy-construction. Both the Predicate (Normally a std::function, or lambda), and custom iterators can have state, which can be expensive to copy. Profiler identified this as a bottleneck while using boost::adaptors::filtered.
The MPL version is slower to compile and `BOOST_STATIC_ASSERT` is
already used in some places. So unify that.
This also fixes `Wzero-as-null-pointer-constant` warnings, see https://github.com/boostorg/mpl/pull/75
The recent commit 5777e9944b broke code such as
(*it++).foo(), where the result of dereferencing would be convertible to
the value type but did not provide the members of the value type. To mitigate
this, return a reference to the value instead of a proxy object. This will only
work for non-writable iterators (and it didn't work for writable iterators
before either) because in that case a proxy is needed to be able to intercept
operator=.
Also fix a similar issue with (it++)->foo() by adding operator-> overloads
to the post-increment result proxies.
Added tests for the fixes.
This allows expressions such as `Iterator it2(it1++)` to compile.
Additionally separated operations that are allowed on the result of
dereferencing the proxy to a separate set of proxies to make the allowed
set of expressions more strict and unambiguous. In particular, it means
`it++` cannot be converted to value type and `*it++` cannot be converted
to the iterator type anymore. Also, make sure `*it1++ = *it2++` works
as expexted by explicitly converting the proxy to the value type on
assignment.
Fixes https://github.com/boostorg/iterator/issues/75.
This fixes incorrect final iterator type being used in iterator_facade, which
results in an internal base class being returned from various facade methods.
Reported in https://github.com/boostorg/iterator/issues/75.
