Re: [boost] [next gen future-promise] What to call themonadicreturntype?

Subject: Re: [boost] [next gen future-promise] What to call themonadicreturntype?
From: Peter Dimov (lists_at_[hidden])
Date: 2015-05-29 18:26:00

Niall Douglas wrote:

>> > It's not that I don't like it, I don't see sufficient motivation for 
>> > it.

Actually I've changed my mind and now I don't like it. It's a catch(...) 
without a rethrow, and while those are occasionally necessary, they are not 
likable.

To be clear, I'm talking about the N4048's .catch_error that takes an 
exception_ptr, not an error_code.

> > I'm also not quite sure how it's to be used. Vicente's wording in N4048 
> > is a bit unclear.
> >
> >     future<X> f1 = async( ... );
> >     future<Y> f2 = f1.catch_error( []( exception_ptr e ) { return 
> > Y(); } );
> >
> > What happens when f1 has a value?
>
> Surely for catch_error() one must always return the same type of future as 
> the input? Otherwise it couldn't work when f1 has a value.

Vicente in N4048 says that it's not required to return the same type.