Tuesday, November 18, 2014

Digest for comp.lang.c++@googlegroups.com - 25 updates in 6 topics

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surabhi@triplepointpr.com: Nov 18 12:08PM -0800

Hi everyone,
 
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@hack_summit
legalize+jeeves@mail.xmission.com (Richard): Nov 18 09:02PM

[Please do not mail me a copy of your followup]
 
surabhi@triplepointpr.com spake the secret code
 
>Extreme Programming, Test Driven Development, Heroku, Spark, Bittorrent,
 
If you're interested in Test-Driven Development for C++, try my workshop
from C++ Now! 2014:
<https://github.com/boostcon/cppnow_presentations_2014/tree/master/files/test_driven>
--
"The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://computergraphicsmuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>
JiiPee <no@notvalid.com>: Nov 18 06:58PM

Is this forum also a place to ask simple questions? Sometimes does not
find answer for something.
 
Anyway here two:
 
1) New C++ has keywords "or" to replace ||. LIke:
 
int a = 6;
if(a == 5 or a > 9)
....
 
(old: if(a == 5 || a > 9) )
 
I really like "or" because its more readable. But is there something
against using it? Why C++ people normally still prefer ||, I don't see
people using "or" ? Is there a reason for it? I like to use all the
improvements as they come with C++ ...
 
2) I found a piece of code:
 
template <typename T, size_t N>
void foo( T(&arr)[N] )
{
// use arr - array...
}
 
and called:
 
int arr[] = {1,2,3};
foo(arr);
 
Been scratching my head with this...
I am not familiar with this syntax T(&arr)[N]. What is that? Why it
takes arr's address (&arr)? Or is it a reference? Also, is this a
template function argument which can automatically find T and N from
array arr when called?
Would like to know that this T(&arr)[N] means. I know N is the size
of the array, but the rest...
 
thanks
red floyd <no.spam@its.invalid>: Nov 18 11:11AM -0800

On 11/18/2014 10:58 AM, JiiPee wrote:
 
> array arr when called?
> Would like to know that this T(&arr)[N] means. I know N is the size
> of the array, but the rest...
 
It's a reference to an array of N elements of type T.
 
A common usage is
 
template<typename T, size_t N>
size_t array_size(T(&arr)[N])
{
return N;
}
JiiPee <no@notvalid.com>: Nov 18 07:31PM

On 18/11/2014 19:21, Martin Shobe wrote:
> is the type of object in the array. Yes, the template function is
> automatically found when the call to foo is compiled.
 
> Martin Shobe
 
ok thanks
JiiPee <no@notvalid.com>: Nov 18 07:35PM

template <typename T, size_t N>
void foo( T(&arr)[N] )
{
// use arr - array...
}
 
and called:
 
int arr[] = {1,2,3};
foo(arr);
 
 
On 18/11/2014 19:21, Martin Shobe wrote:
 
> Yes, the template function is automatically found when the call to
> foo is compiled.
 
I meant the foo function is able to automatically know T and N from the
call
 
foo(arr);
 
So obviously arr carries with it the information of its size and its
elements type I guess. Thats how foo know them.
JiiPee <no@notvalid.com>: Nov 18 07:38PM

On 18/11/2014 19:11, red floyd wrote:
> {
> return N;
> }
 
oh cool , this was new to me. The way to get the size of an array.
JiiPee <no@notvalid.com>: Nov 18 07:46PM

On 18/11/2014 19:21, Martin Shobe wrote:
 
> Other than that, I continue to use || because it's what I expect to
> see when reading C++.
 
Ok, but do you agree that:
 
if( a == 5 or a == 8 )
 
is more human readable than
 
if( a == 5 || a == 8 )
 
?
we are really doing or-operation there, so how could something else than
or be better?
scott@slp53.sl.home (Scott Lurndal): Nov 18 08:08PM


>if( a == 5 or a == 8 )
 
>is more human readable than
 
>if( a == 5 || a == 8 )
 
Having two ways to do the same thing in a single language wasn't
a good idea. In fact, this 'or' in C++ is a spectacularly bad idea.
 
Many of us don't have the option of using a newer compiler, or must
use many different versions of compilers (for various reasons) and
for that reason alone cannot (and will not) use 'or' in place of the
conditional-OR operator.
"Rick C. Hodgin" <rick.c.hodgin@gmail.com>: Nov 18 12:10PM -0800

On Tuesday, November 18, 2014 2:47:00 PM UTC-5, JiiPee wrote:
> if( a == 5 or a == 8 )
 
> is more human readable than:
> if( a == 5 || a == 8 )
 
I would say for most C/C++ developers, reading || and && are so
second nature now that it's not any easier to read. But for
newcomers to the language, and in moving forward, having the
or,and make sense.
 
I think there should also be xor, not, neg.
 
Best regards,
Rick C. Hodgin
"Rick C. Hodgin" <rick.c.hodgin@gmail.com>: Nov 18 12:12PM -0800

On Tuesday, November 18, 2014 3:08:44 PM UTC-5, Scott Lurndal wrote:
> use many different versions of compilers (for various reasons) and
> for that reason alone cannot (and will not) use 'or' in place of the
> conditional-OR operator.
 
I'm not sure it's a good idea to maintain like unto the past because
there are ways to do things in the present which are incompatible with
the way things were done in the past. I think the goal should always
be looking forward, not looking backward.
 
Best regards,
Rick C. Hodgin
Wouter van Ooijen <wouter@voti.nl>: Nov 18 09:28PM +0100

Martin Shobe schreef op 18-Nov-14 9:08 PM:
> only means or in English (okay maybe there are other languages). Someone
> who speaks French might find using the word for gold rather odd. Symbols
> don't usually carry such baggage.
 
That hypotetical frenchman would have to get used to English anyway (if
then else do operator class template namespace throw catch ...).
 
Wouter van Ooijen
(Dutch)
JiiPee <no@notvalid.com>: Nov 18 08:44PM

On 18/11/2014 20:12, Rick C. Hodgin wrote:
> be looking forward, not looking backward.
 
> Best regards,
> Rick C. Hodgin
 
I agree. When I make code nowadays, am not trying make it so that it
would also compile with gnu 2.1 from 1995 :).
 
But obviously some are forced to do that.
 
I also agree that its not good to have two ways to do this thing. But
"or" should have been the first choice even 1985 ... imo.
JiiPee <no@notvalid.com>: Nov 18 08:46PM

On 18/11/2014 20:08, Martin Shobe wrote:
> Someone who speaks French might find using the word for gold rather
> odd. Symbols don't usually carry such baggage.
 
> Martin Shobe
 
but they use "or" in other languages.. for example visual basic uses
it... so it is a good candidate
JiiPee <no@notvalid.com>: Nov 18 08:47PM

On 18/11/2014 20:28, Wouter van Ooijen wrote:
> (if then else do operator class template namespace throw catch ...).
 
> Wouter van Ooijen
> (Dutch)
 
yes agree.
Also there are many other keywords also which are in english, like for,
do, ... almost all. So I do not see this argument being good in that way.
JiiPee <no@notvalid.com>: Nov 18 08:50PM

On 18/11/2014 20:10, Rick C. Hodgin wrote:
 
> I think there should also be xor, not, neg.
 
> Best regards,
> Rick C. Hodgin
 
"not" is there already :)
Robert Hutchings <rm.hutchings@gmail.com>: Nov 18 12:52PM -0600

Since I will be accessing a MySQL database, I was wondering if there are
any C++-specific object-relational mapping libraries out there? I
Googled and found a couple, but I wondered if anyone here is using one?
legalize+jeeves@mail.xmission.com (Richard): Nov 18 08:27PM

[Please do not mail me a copy of your followup]
 
Robert Hutchings <rm.hutchings@gmail.com> spake the secret code
 
>Since I will be accessing a MySQL database, I was wondering if there are
>any C++-specific object-relational mapping libraries out there? I
>Googled and found a couple, but I wondered if anyone here is using one?
 
I haven't actually used it, but the one that struck me as the one I'd
like to use was odb: <http://www.codesynthesis.com/products/odb/>
--
"The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://computergraphicsmuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>
Robert Hutchings <rm.hutchings@gmail.com>: Nov 18 02:33PM -0600

On 11/18/2014 2:27 PM, Richard wrote:
>> Googled and found a couple, but I wondered if anyone here is using one?
 
> I haven't actually used it, but the one that struck me as the one I'd
> like to use was odb: <http://www.codesynthesis.com/products/odb/>
 
That was the one I liked when I googled around....
"Öö Tiib" <ootiib@hot.ee>: Nov 17 04:01PM -0800

On Monday, 17 November 2014 23:34:40 UTC+2, Scott Lurndal wrote:
> component (e.g. libstdc++.so.6 on linux) is dynamically linked,
> most benefit would accrue sans recompilation by simply updating
> the library to a newer version.
 
How? Big part of C++ standard libraries is implemented in include
files. C++ library can't be replaced without recompiling.
 
> for most real-world projects; given internal dependencies, third-party
> dependencies, the effort required to requalify any non-trivial
> application with the new compilation tools and the cost of labor.
 
I did not say that it is cost-free. I said that Vincenzo was correct
that recompiling C++98 code with C++11 compiler does often improve
product's performance. If serious maintenance works are in plan anyway
then the switch is possibly worth it. Also most of the developers
actually like to switch to more modern tools. It tends to add to
success when the involved engineers do like what is going on.
Jorgen Grahn <grahn+nntp@snipabacken.se>: Nov 18 08:30AM

On Mon, 2014-11-17, Richard wrote:
 
> One might as well ask:
 
> Since C++ can be transformed into C, what is the point?
 
> The point is that using C++ allows us to get the job done at a higher
...
[snip]
 
You seem to misunderstand my question: I don't question the usefulness
of C++ or C++11. My question above was
 
What would be the point of automating it?
^^^^^^^^^^^^^^^^
 
/Jorgen
 
--
// Jorgen Grahn <grahn@ Oo o. . .
\X/ snipabacken.se> O o .
legalize+jeeves@mail.xmission.com (Richard): Nov 18 05:48PM

[Please do not mail me a copy of your followup]
 
Jorgen Grahn <grahn+nntp@snipabacken.se> spake the secret code
 
>You seem to misunderstand my question: I don't question the usefulness
>of C++ or C++11. My question above was
 
> What would be the point of automating it?
 
Automated refactorings can be applied over a large code base quickly
and are (usually) less error prone.
 
Specifically, with clang-modernize you should read the documentation
on the provided refactorings. Not all of them are perfect; replacing
auto_ptr with unique_ptr or applying the call-by-value transformations
might best be applied with some oversight.
 
Some people consider excessive use of 'auto' to be obfuscating.
 
I'm not aware of anyone complaining about the range for loop
transformation however.
 
Having done lots of refactoring of C++ code by hand, I can tell you
that being able to apply refactorings in an automated manner is almost
always preferable.
 
The only caveat is that you have to be able to trust your refactoring
tool. Many refactoring tools do refactorings on an ad-hoc basis and
can introduce errors. This is why I created a test suite for C++
refactoring tools:
<https://github.com/LegalizeAdulthood/refactor-test-suite>
<http://legalizeadulthood.wordpress.com/2014/06/13/refactoring-test-results-for-vax-10-8-2036-0-built-2014-05-22/>
<http://legalizeadulthood.wordpress.com/2010/02/02/c-refactoring-tools-test-suite-available/>
 
Since clang-modernize uses a *real* C++ parser that is used by a
production quality compiler in order to extract information about the
source code, it is much more reliable and trustworthy than tools that
use ad-hoc parsing or a parser that isn't used to actually compile
real-world C++ code.
--
"The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://computergraphicsmuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>
Louis Krupp <lkrupp@nospam.pssw.com.invalid>: Nov 18 08:37AM -0700

On Mon, 17 Nov 2014 13:52:51 -0800 (PST), Robert Hutchings
<rm.hutchings@gmail.com> wrote:
 
<snip>
 
>Louis, how did you get the PDF download AND the paperback book? Was this on http://shop.oreilly.com?
 
Yes. I followed the link in your original post (thank you for that,
by the way), and I clicked on "Print & Ebook" under "Buying Options"
on the top right.
 
Louis
Robert Hutchings <rm.hutchings@gmail.com>: Nov 18 09:55AM -0600

On 11/18/2014 9:37 AM, Louis Krupp wrote:
> by the way), and I clicked on "Print & Ebook" under "Buying Options"
> on the top right.
 
> Louis
 
Okay, I didn't see that. Maybe I can still get the book if I have
purchased the PDF download...
David Brown <david.brown@hesbynett.no>: Nov 18 09:23AM +0100

On 17/11/14 18:30, red floyd wrote:
>> analysis tool.
 
>> http://cppcheck.sourceforge.net/
 
> And isn't splint still around, too?
 
I don't think splint ever handled C++. And to my knowledge, its
development stalled over 10 years ago.
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