Idea: break/continue and scope guards

[BCS]

mike wrote:
> Hi!
> 
> Don't know if that makes any sense or if it would be of any use, but I had an idea lately and wanted to share it here, maybe it's some little thing that could be nice in D.
> 
> So here we go:
> 
> ' foreach (customer; customerList)
> ' {
> '     foo(customer);
> '     scope(failure) foo_rollback(customer);
> '
> '     bool ok = check_valid_after_foo(customer);
> '     if (!ok) continue(failure);
> '
> '     commit(customer);
> ' }
> 
> Basically the idea is to trigger the appropriate scope guards when a break or continue occurs. Another thing where this could be handy is in situations where you loop over an array to search for a specific item and do something when it is found, like:
> 
> ' foreach (customer; customerList)
> ' {
> '     scope(success) result = customer;
> '     if (customer.ID == wantedID) break(success);
> ' }
> 
> What do you think?
> 
> -mike

[posted in D and D.announce NG, please reply in D ng]

This is much like an idea I had, but backwards from the way I thought of 
it. Add more options to scope, not break/continue.

the second code example would work like this the way I thought of.

' foreach (customer; customerList)
' {
'     scope(break) result = customer;
'     if (customer.ID == wantedID) break;
' }


other scope "types":
goto            // exit by goto
goto : label    // exit by goto to a given label
continue        // duh
enter           // execute on entrance by any means (goto, switch, etc.)
out             // used in a loop same as exit but for scope including
                 // loop. Note: scope(exit) in a loop runs on each cycle,
                 // 'out' would only run at the end of the last cycle.