On Sun, May 31, 2015 at 6:25 PM, Vicente J. Botet Escriba
Le 30/05/15 22:49, Peter Dimov a écrit :
Vicente J. Botet Escriba wrote:
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.
If I said that it was an error. Could you point me where?
Input Parameters: • Lambda function: The lambda function on map()/bind() takes a future<t>::value_type. The lambda function on catch_error() takes an exception_ptr. Both could return whatever type. This makes propagating exceptions straightforward. This approach also simplifies the chaining of continuations.
Thanks. I suspect I was referring to map and bind. future<T>::cath_error must return T or future<T>. I recognize that it is not clear in the N4048.
Initially catch_error() was called recover(). It can be used to recover from errors and then the function returns a value or a future ready with a value and also to change the reported error, in this case the function should return future<T> ready with an exception.
I can imagine catch_error() returning something _convertible_
future<X> f1 = async( ... ); future<Y> f2 = f1.catch_error( []( exception_ptr e ) { return Y(); } );
Y needs to be convertible from X. Not sure there is much value in that, however. P.S. can I specialize std::future<MyType> ? And does that just cause headaches for the STL? Tony