On 2010-03-04 11:02 AM, Alf P. Steinbach wrote:
* Robert Kern:
On 2010-03-04 09:48 AM, Alf P. Steinbach wrote:
* Jean-Michel Pichavant:
Alf P. Steinbach wrote:
From your post, the scope guard technique is used "to ensure some
desired cleanup at the end of a scope, even when the scope is exited
via an exception." This is precisely what the try: finally: syntax
is for.
You'd have to nest it. That's ugly. And more importantly, now two
people in this thread (namely you and Mike) have demonstrated that
they do not grok the try functionality and manage to write incorrect
code, even arguing that it's correct when informed that it's not, so
it's a pretty fragile construct, like goto.
You want to execute some cleanup when things go wrong, use try except.
You want to do it when things go right, use try else. You want to
cleanup no matter what happen, use try finally.
There is no need of any Cleanup class, except for some technical
alternative concern.
Have you considered that your argument applies to the "with" construct?
You have probably not realized that.
But let me force it on you: when would you use "with"?
When there is a specific context manager that removes the need for
boilerplate.
That's "cleanup no matter what happen".
For the "# Do stuff" block, yes. For the initialization block, you can write a
context manager to do it either way, as necessary.
Check if that case is covered by your argument above.
Now that you've been told about the "with" angle, don't you think it's a
kind of weakness in your argument that it calls for removing "with" from
the language?
No, it only argues that "with Cleanup():" is supernumerary.
I don't know what "supernumerary" means,
http://www.merriam-webster.com/dictionary/supernumerary
but to the degree that the
argument says anything about a construct that is not 'finally', it says
the same about general "with".
He's ignorant of the use cases of the with: statement, true. Given only your
example of the with: statement, it is hard to fault him for thinking that try:
finally: wouldn't suffice.
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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