Re: [review][LEAF] Review of LEAF starts today : May 22 - May 31

From: Peter Dimov (pdimov_at_[hidden])
Date: 2020-05-31 17:55:29

Rainer Deyke wrote:
> Here is one use case for some kind of low-level access to error objects 
> without going through lambdas (although it would have a different form 
> than the one used by Bjorn).  Suppose I have an error type that may or may 
> not be annotated with a file name, an IP address, or a user name, 
> individually or in any combination.  For each of these annotations, I want 
> to handle it the same whenever it is present, regardless of the others. 
> Without some sort of direct access to error objects, the code for this 
> would look something like this:
>
> return leaf::try_handle_some(
>    some_try_block,
>    [](leaf::match<my_error>,
>       leaf::e_file_name fname,
...

I think that you can match by pointer here:

>       leaf::e_file_name * fname,

which will give you nullptr if the file name isn't present.