scope guards (Re: Ideas regarding flow control and loops)

[Bruce Adams]

> >
> I see I needed to RTFM. I see you are suggesting an extension to >existing syntax I missed. Still it makes me uneasy. Overuse of this >feature will make for very hard to read code. scope(exit) serves a >very particular purpose to replace RAII where destructors can't be >used because of GC. I don't actually get scope(success) and >scope(failure) yet (have to RTFM some more). success and failure of >what exactly? The page eplicitly says scope doesn't catch >exceptions. Its only for replacing the finaly of a try catch finally.

Right I have found after some digging Andrei Alexandrescu's
original suggestion.

"I believe three constructs would simplify writing robust code: 

1. on_scope_exit { ... code .. } 

Executes code upon the current scope's exit. Several on_scope_exit 
blocks in a scope are executed LIFO. 

2. on_scope_success { ... code ... } 

Executes code if the current scope is exited normally (no exception 
engendered). 

3. on_scope_failure { ... code ... } 

Executes code if the current scope is exited via an exception.
"

All specifically to do with exception safety.
Its mentioned in passing on at least two pages (links below) but lacking (as far as I can see lacking a clear definition like this on the digital mars web-site.

http://www.digitalmars.com/d/statement.html
http://www.digitalmars.com/d/exception-safe.html