[PATCH] D79740: Align mapped_iterator::reference type with mapped_iterator::operator*() return value.

[Ivan Kelarev via Phabricator via llvm-commits]

ikelarev added a comment.

> Any chance you've looked into prior art (I assume Boost has something like this) with regards to when/how often the functor should be called?

David, as I can see, in boost transform_iterator calls the functor directly every time operator* is called.

More detailed, transform_iterator does not impelement operator* itself, it just have dereference() method which returns m_f(*this->base()) value. operator* is implemented in iterator_facade class, the base class of iterator_adaptor class which is base class of transform_iterator. iterator_facade class operator* implementation just returns iterator_core_access::dereference(this->derived()) value, where iterator_core_access::dereference method (declared in auxiliary iterator_core_access class) just calls f.dereference() method.

I used this source codes: https://github.com/boostorg/iterator/tree/develop/include/boost/iterator


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