Negative

[xs0]

Andrew Fedoniouk wrote:
> I am with Charles here...
> 
> I don't understand why
> on_scope_failure & co. are significantly better than
> try catch finally?

imho, they're not better in all cases, just in some :)

> What is wrong with them?

nothing

> Semantically try-catch-finally are well known and
> widely recognizable constructions.

agreed

> BTW: Am I right in my assumption that
> proposed on_scope_exit / on_scope_success / on_scope_failure
> is a direct equivalent of the following:
> 
> try
> {
>    [scope code]
>    my_on_scope_success().
> }
> catch(...)
> {
>    my_on_scope_failure().
> }
> finally {
>   my_on_scope_exit().
> }
> 
> If yes then again what it wrong with them in principle?

Well, nothing in principle, but like it was said already:
- init and cleanup can be close together (which is good in itself)
- as a consequence, it's harder to forget cleanup
- it's prettier - code that is about linear looks like it's about linear 
(see example 2)
- you can reorder them as you see fit (see example 1)
- less typing :)


Example 1:

=======================
on_scope_exit foo();
on_scope_failure bar();
on_scope_exit baz();

// code
=======================

Versus

=======================
try {
     try {
         try {
             // code
         } finally {
             baz();
         }
     } catch (Object e) {
         bar();
         throw e;
     }
} finally {
     foo();
}
=======================


Example 2:

==================================
// notice how creation and cleanup are together
Logger log = getLogger();
on_scope_exit log.close();
on_scope_failure log.logFailure("...");

File outf = getOutputFile();
on_scope_exit outf.close();

File inf = getInputFile();
on_scope_exit inf.close();

File tmpf = createTempFile();
on_scope_exit tmpf.delete();
on_scope_exit tmpf.close();

// lots of code
==================================

Versus

==================================
Logger log = getLogger();
try {
     File outf = getOutputFile();
     try {
         File inf = getInputFile();
         try {
             File tmpf = createTempFile();
             try {
                 // lots of code
             } finally {
                 tmpf.close();
                 tmpf.delete();
             }
         } finally {
             inf.close();
         }
     } finally {
         outf.close();
     }
} catch (Object e) {
     log.logFailure("...");
     throw e;
} finally {
     log.close();
}
==================================