Monday, May 18, 2015

Digest for comp.lang.c++@googlegroups.com - 15 updates in 5 topics

Juha Nieminen <nospam@thanks.invalid>: May 18 09:39AM

> return overlay{ 1 }.b.a; }
 
> int main()
> { ::std::cout << "endian()" << " = " << endian() << '\n'; }
 
test.cc:2:16: error: constexpr function never produces a constant expression
[-Winvalid-constexpr]
constexpr bool endian()
^
test.cc:5:23: note: read of member 'b' of union with active member 'i' is not
allowed in a constant expression
return overlay{ 1 }.b.a; }
 
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scott@slp53.sl.home (Scott Lurndal): May 18 01:45PM

>I didn't find an approach I liked so I rely on users to read=20
>the documentation and set -DCMW_BIG_ENDIAN if necessary. From
>what I can tell, big-endian systems are fading from the landscape.
 
Not true at all. Consider that network byte-order is big-endian,
and you'll see why big-endian is still quite popular in networking
applications (routers, switches, security appliances, etc). Note
that the new ARM64 processor is capable of operating in either
(or both) endiannesses.
woodbrian77@gmail.com: May 18 12:15PM -0700

On Monday, May 18, 2015 at 8:45:56 AM UTC-5, Scott Lurndal wrote:
> applications (routers, switches, security appliances, etc). Note
> that the new ARM64 processor is capable of operating in either
> (or both) endiannesses.
 
That might be interesting if it were a big-endian only device.
 
 
Brian
Ebenezer Enterprises - In G-d we trust.
http://webEbenezer.net
Sam <sam@email-scan.com>: May 17 08:07PM -0500

> removed ? (in a sense of not just not having to use a feature or a paradigm,
> but also not having to deal with it or consider it's use by others)
 
> Thanks
 
When is his homework assignment due? What class is this, where you get
questions like this, leading up to your final exams?
woodbrian77@gmail.com: May 17 06:35PM -0700

> Hope everyone for a nice weekend,
 
> Defining programmers as those who authored any amount of C++ code that made it into production environment -
> If you could add one thing - anything at all - to the core language or the new standard, what would it be ?
 
I mentioned this in another thread, but I'd like to see a ctor
added to std::string that takes a char const* and an integer
value. The integer would be the length to reserve beyond the
length of the char const*. I think this ctor would help to
reduce the number of allocations strings do. It's surprising
to me that this wasn't added years ago. Better late than never.
 
I look forward to modules being added.
 
Brian
Ebenezer Enterprises - In G-d we trust.
http://webEbenezer.net
Paavo Helde <myfirstname@osa.pri.ee>: May 17 11:28PM -0500

udtelco@gmail.com wrote in
> like to see removed ? (in a sense of not just not having to use a
> feature or a paradigm, but also not having to deal with it or consider
> it's use by others)
 
1. Portable C++ ABI (something along the lines of e.g.
https://isocpp.org/files/papers/n4028.pdf)
 
2. Automatic conversions (numeric-to-bool, enum-to-numeric, numerics
themselves (though the last one is tricky, just slapping an explicit
static_cast everywhere where a conversion is required would make the things
even worse)).
udtelco@gmail.com: May 17 09:57PM -0700

On Sunday, May 17, 2015 at 9:07:34 PM UTC-4, Sam wrote:
 
> When is his homework assignment due? What class is this, where you get
> questions like this, leading up to your final exams?
 
Who is "he", and what's bothering you so much about this question ? And do you always stick an attachment into your contribution to this global museum of wisdom and tolerance ?
Christopher Pisz <nospam@notanaddress.com>: May 18 10:15AM -0500

> If you could add one thing - anything at all - to the core language or the new standard, what would it be ?
> And in a same way, but trickier, what if anything would you like to see removed ? (in a sense of not just not having to use a feature or a paradigm, but also not having to deal with it or consider it's use by others)
 
> Thanks
 
Add:
datetime more like boost's
timezone not like boost's
exceptions with call stack built in
ability to see "who started the thread" when debugging
naming of threads
 
Remove:
globals
goto
variadic argument lists
C
 
 
--
I have chosen to troll filter/ignore all subthreads containing the
words: "Rick C. Hodgins", "Flibble", and "Islam"
So, I won't be able to see or respond to any such messages
---
Victor Bazarov <v.bazarov@comcast.invalid>: May 18 11:23AM -0400

On 5/18/2015 11:15 AM, Christopher Pisz wrote:
 
> Remove:
> [..]
> C
 
That way we'll end up with the language called "++", which is neither
here nor there. ;-)
 
V
--
I do not respond to top-posted replies, please don't ask
"Jason C. McDonald" <indeliblebluepen@nospam.invalid>: May 18 11:39AM -0700

On 05/18/2015 08:23 AM, Victor Bazarov wrote:
 
> That way we'll end up with the language called "++", which is neither
> here nor there. ;-)
 
> V
 
So...we once had the attack of the one-letter languages. Now we'll have
the attack of the non-alphanumeric languages?
 
++
-- (for the minimalists)
?? (for absolutely beginners)
!! (for quick-and-dirty programming by people who reject all standards)
!%#*&@^ (for irritating the heck out of people)
 
--
Jason C. McDonald (CodeMouse92)
[CEO, Lead Dev @ MousePaw Games]
udtelco@gmail.com: May 17 09:45PM -0700

I would like to have sort function for strings that would first compare length and have longer string be greater then shorter one, and if they are same length - compare them as usual. So that
 
1. "1234567"
2. "12345"
3. "111111"
4. "13456"
5. "01102121"
 
would get sorted as
5 > 1 > 3 > 4 > 2
 
bool less(const string& lhs, const string&rhs)
{
// if( lhs.length() < rhs.length() ) return true;
return (lhs.length() < rhs.length()) ? true : (lhs < rhs);
}
 
Is there a more efficient way to do this ?
 
Thank you dear newsgroup.
"Öö Tiib" <ootiib@hot.ee>: May 17 11:16PM -0700

> // if( lhs.length() < rhs.length() ) return true;
> return (lhs.length() < rhs.length()) ? true : (lhs < rhs);
> }
 
So both 'less( "1234567", "13456" )' and
'less( "13456", "1234567" )' return 'true'?
 
> Is there a more efficient way to do this ?
 
Why you care about efficiency when your algorithm seems incorrect?
Most important goal is always correctness since no one needs
software that gives incorrect answers more quickly.
Juha Nieminen <nospam@thanks.invalid>: May 18 09:46AM

> // if( lhs.length() < rhs.length() ) return true;
> return (lhs.length() < rhs.length()) ? true : (lhs < rhs);
> }
 
That doesn't work because if lhs is larger than rhs, then they won't
be compared by length. What you want is:
 
return (lhs.length() == rhs.length()) ? (lhs < rhs) :
(lhs.length() < rhs.length());
 
The compiler will most probably optimize those extra length() calls
away, so there's usually no need to worry about them. (And even if it
doesn't, it's not a big deal anyway.)
 
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legalize+jeeves@mail.xmission.com (Richard): May 18 02:39AM

[Please do not mail me a copy of your followup]
 
Paul <pepstein5@gmail.com> spake the secret code
>struct A {
> operator B();
>};
 
struct A is defining a conversion operator so that it can be converted
into a struct B. This enables the following:
 
A a;
B b1 = a; // implicit conversion
B b2 = static_cast<B>(a); // explicit conversion
 
If you change to:
 
struct B;
struct A {
explicit operator B();
};
 
A a;
B b1 = a; // error: implicit conversion not allowed
B b2 = static_cast<B>(a); // OK: explicit conversion
--
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The Computer Graphics Museum <http://computergraphicsmuseum.org>
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Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>
legalize+jeeves@mail.xmission.com (Richard): May 18 02:30AM

[Please do not mail me a copy of your followup]
 
Chicken Mcnuggets <chicken@mcnuggets.com> spake the secret code
 
>and this is what I was roughly hoping to emulate. The URL regex and the
>views are provided by the user and the framework provides the code to
>link the two together.
 
I'm familiar with Django and how it maps URLs to views.
 
There are a number of ways to orchestrate the C++ equivalent.
 
For instance:
 
class IView {
public:
virtual ~IView() {}
 
// user implements this
virtual void render() = 0;
};
 
std::map<std::string, std::unique_ptr<IView>> viewMapping;
 
Really, you want to define an abstraction for your C++ customers to
implement so that you are employing Dependency Inversion Principle
and eliminating unnecessary coupling.
 
Their callback handler is a detail that depends on an abstraction (IView).
 
Your regex->handler dispatcher is a detail that depends on an abstraction
(IView).
 
You publish the IView interface for your clients to implement.
--
"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>
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