Re: [boost] [optional] Safe optional

On Thu, Nov 20, 2014 at 11:00 AM, Andrzej Krzemienski wrote:

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Note that the proposed expected has the same "identity crisis":

It'll probably face the same resistance. Comparing no value and a value simply doesn't make sense and code like shown is a real bug.

I disagree with this statement. In case of optional<T> having no value of T is deliberately treated as a yet another value. This has a well defined purpose. It is covered in the documentation here: http://www.boost.org/doc/libs/1_57_0/libs/optional/doc/html/boost_optional/q...

By containers you specifically mean map, right? Unordered map for example would not require operator< Containers (maps) always come up as the primary rationale for operator< However, the user could also define his own comparison function for this purpose. Perhaps other use cases of operator< could be presented.

the docs also recommends NOT to use optional<T> to signal a potential error/difficulty in computing T: http://www.boost.org/doc/libs/1_57_0/libs/optional/doc/html/boost_optional/t... .

This is the choice made for optional<T>. The authors of expected may want to choose a different model.

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What's wrong with being explicit with what you want, especially in ambiguous situations like those mixed comparisons?

Nothing wrong with that. It is just not the job for optional. Perhaps a job for expected.

But is it what people have problems with isn't it? -- Olaf