Comparison to TartanLlama/expected

[bryceschober]

It would be nice to see a feature comparison against TartanLlama/expected, and maybe consider some of his functional extensions.

[martinmoene]

There's a branch with an initial implementation of D0786: ValuedOrError and ValueOrNone types.

[viboes]

This doesn't address yet the monadic operations that TartanLlama/expected, includes as member functions. The original paper/implementation included such monadic operations. [original version] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0323r0.pdf [original ref_impl] https://github.com/viboes/std-make/tree/master/include/experimental/fundamental/v3/expected

The last reference implementation doesn't include them. [ref_impl] https://github.com/viboes/std-make/tree/master/include/experimental/fundamental/v3/expected2

For the monadic operations, the last not-yet-reviewed revision is at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0650r2.pdf

I understand the advantage of the member function to be able to chain operations. I believed the LEWG wanted non-member function, but I misunderstood surely. With UFCS we will not have to discuss this ;-) We will see what do we have at the end.