Re: [boost] [iterator] function_output_iterator constructed from a lambda function is not assignable

On Sunday, February 14, 2016 at 9:18:15 PM UTC-6, Peter Dimov wrote:

Paul Fultz II wrote:

...

One way to deal with this is to put it into boost::optional.

boost::optional<T> uses T::operator= when the source and the target hold a value.

It seems that boost::optional is not constrained properly, the following compiles just fine: struct not_assignable { not_assignable& operator=(const not_assignable&)=delete; }; static_assert(!std::is_copy_assignable(), "Assignable"); static_assert(std::is_copy_assignable>(), "Not Assignable"); However, if I use the assignment operator, it breaks with a compile error. Either way `boost::optional` should fallback on in-place new, when there is no assignment operator.

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