Re: [boost] Final lightweight monad, next gen futures and upcoming AFIO review

On 28 Jun 2015 at 21:05, Michael Marcin wrote:

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I mean: result is like "give me T or it's an error". There is no empty state. Empty would already be an error state. I'd only understand empty if it's an async operation that didn't finish already.

What's the state of a default constructed result?

Is it an error state? Is it empty? Or is it not default constructible?

In my dirty monad, result<T> (there is no result) is always default constructed to empty. If you want it constructed to something else, simply pass that into its constructor. There is also a make_monad(T/error_code/exception_ptr). In Rust's Result, there is no default construction. You must choose either a T or a E at the point of construction, failure to do so is a compile time error. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/