Friday, May 6, 2016

Digest for comp.lang.c++@googlegroups.com - 11 updates in 6 topics

Ralf Goertz <me@myprovider.invalid>: May 06 10:13AM +0200

Am Wed, 4 May 2016 16:26:09 +0000 (UTC)
 
> >auto it=std::find(v.begin(),v.end(),value);
 
> It's coming.
 
> <http://ericniebler.com/2014/10/11/n4128-ranges-for-the-standard-library/>
 
That's exactly what I was hoping for, thanks.
legalize+jeeves@mail.xmission.com (Richard): May 06 04:14PM

[Please do not mail me a copy of your followup]
 
Ralf Goertz <me@myprovider.invalid> spake the secret code
 
>> It's coming.
 
>> <http://ericniebler.com/2014/10/11/n4128-ranges-for-the-standard-library/>
 
>That's exactly what I was hoping for, thanks.
 
Depending on your compiler you can use the library today:
<https://github.com/ericniebler/range-v3>
 
It needs more SFINAE support than VS 2015 Update 2 is currently
offering, but I'm sure MS is working on improving that.
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bleachbot <bleachbot@httrack.com>: May 06 02:03AM +0200

bleachbot <bleachbot@httrack.com>: May 06 02:42AM +0200

ram@zedat.fu-berlin.de (Stefan Ram): May 06 01:57AM

> text_buffer_.handle, impl::winapi::Output_flags::Enum()
> );
> }
 
I don't get it. What does this that the following does not?
 
Impl( const Point size )
: text_buffer_()
, info_( text_buffer_.handle )
, text_buffer_activation_( text_buffer_.handle )
{
{
Console_info params = info_.api_info();
 
params.dwSize = {short( size.x ), short( size.y )};
params.dwCursorPosition = {};
//screen.wAttributes = bitsForBgFg(
params.srWindow = {0, 0, short( size.x - 1 ), short( size.y - 1 )};
params.dwMaximumWindowSize = params.dwSize;
info_.make_real( params );
}
impl::winapi::set_output_mode(
text_buffer_.handle, impl::winapi::Output_flags::Enum()
);
}
 
Regarding lambdas and withs, I'd have thought more in the
direction of
 
#include <stdio.h>
#include <functional>
 
void with_open_file
( const char * const filename, const char * const mode,
::std::function<void(FILE *)> client )
{ FILE * f = fopen( filename, mode );
if( f )client( f );
fclose( f ); }
 
int main()
{ with_open_file( "C:\\example\\test.txt", "w",
[]( FILE * f ){ fprintf( f, "test\n" ); }); }
 
Of course, in C++ this style of withs todays is needed
rarely because in C++ RAII is a better solution of the
same problem. But this is what a with is to me.
ram@zedat.fu-berlin.de (Stefan Ram): May 06 02:27PM

>You're right, a simple curly braces block with appropriate comment is
>equally clear.
 
In a couse, a participant once asked be about the meaning
of a programm like
 
int main()
{ auto x{ 1 };
{ x = 2; } /**/
/* what is the value of x here? */ }
 
. He wanted to know whether the assignment was abolished by
the »} /**/«. I replied that it was not abolished by the »} /**/«.
 
But today, we can have something like this:
 
int main1()
{ auto x{ 1 };
[ = ]() mutable { x = 2; } /**/ ();
/* what is the value of x here? */ }
 
In the program directly above, the »} /**/« in fact /does/
abolish the assignment of »2« to »x«, and »x« is »1« again
at »/* what is the value of x here? */«.
 
Maybe someday this will come in handy for something.
"Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com>: May 06 03:32AM +0200

I just now found occasion to use a lambda expression as a "with"-block:
 
Impl( const Point size )
: text_buffer_()
, info_( text_buffer_.handle )
, text_buffer_activation_( text_buffer_.handle )
{
[&](){
Console_info params = info_.api_info();
 
params.dwSize = {short( size.x ), short( size.y )};
params.dwCursorPosition = {};
//screen.wAttributes = bitsForBgFg(
params.srWindow = {0, 0, short( size.x - 1 ), short( size.y
- 1 )};
params.dwMaximumWindowSize = params.dwSize;
info_.make_real( params );
}();
impl::winapi::set_output_mode(
text_buffer_.handle, impl::winapi::Output_flags::Enum()
);
}
 
(The Hungarian notation names are Microsoft's, not mine. Side note: what
does one call something when Microsoft calls it "info"? In this case
it's a set of values that specify the properties of a console.)
 
Yes, it's a far cry from a dedicated syntax, but still it gets the job done.
 
At one time in the C++03 days I created an awesome WITH macro based on
"for" I think it was, but I never used it more than the original single
use case...
 
 
Cheers,
 
- Alf
"Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com>: May 06 12:41PM +0200

On 06.05.2016 03:57, Stefan Ram wrote:
> text_buffer_.handle, impl::winapi::Output_flags::Enum()
> );
> }
 
You're right, a simple curly braces block with appropriate comment is
equally clear.
 
It was a late night posting, sorry. I had planned to have the "params"
variable, the logical "with" variable, as a default-initialized formal
argument to the lambda. But the initializer expression, using a member
variable, can't be used as initializer for a formal argument because the
outer this can't be captured in the formal argument list.
 
So it was like triple dumb, sorry. But when I posted it it looked neat. :)
 
 
 
> Of course, in C++ this style of withs todays is needed
> rarely because in C++ RAII is a better solution of the
> same problem. But this is what a with is to me.
 
Yes yes.
 
 
Cheers!, & thanks,
 
- Alf
Jorgen Grahn <grahn+nntp@snipabacken.se>: May 06 06:23AM

On Thu, 2016-05-05, Heinz-Mario Frühbeis wrote:
 
>> More generally, please describe the goal you are trying to achieve and
>> why you think this specific task is the way to achieve it.
 
> Isn'T it self-declaring?
 
No. He asked for a use case.
 
And I suspect he asked because
 
a) He didn't really understand what you want (I didn't either).
 
b) If you show your real-life problem, people will be familiar with it
and tell you how they deal with it. It's not unlikely that someone
has a different, better solution.
 
Do you perhaps have a Python background? People here have experience
mapping Python solutions to C++ solutions, too.
 
 
> Currently I use void* to store a member in a vector and I, if used, cast
> this void-pointer into a template-function. This works, (IMHO) less
> coding...
 
/Jorgen
 
--
// Jorgen Grahn <grahn@ Oo o. . .
\X/ snipabacken.se> O o .
Ramine <ramine@1.1>: May 05 08:43PM -0700

Hello......
 
 
I have come to an interesting subject ?
 
This time about softwares..
 
As you have noticed i have described also computer programming
as Petri Nets and there is a proof that Petri Nets with
inhibitor arcs have the same power an expressiveness as
a Turing machine.. now i think there is a weakness in the software
industry, since we can make software products much
more faster than hardware products by automating it, i think
that there is a risk that a minority of us software engineers
will monopolize the industry of softwares, because i think
since we are automating it faster and faster using fewer programmers,
this risk is lesser i think than the hardware industry.
 
 
 
Thank you,
Amine Moulay Ramdane.
Ramine <ramine@1.1>: May 05 08:06PM -0700

Hello,
 
 
Now i have come to an interesting subject..
 
What is computer programming and is it a science ?
 
I was just thinking about this question and since i am
a guy who specializes in parallel programming, i will
answer this question this way:
 
I have done Petri Nets and there is a proof that Petri Nets
with inhibitor arcs have the same power and expressiveness
as a Turing machine, so i think that computer programming is
like constructing Petri Nets or is like constructing automata,
i think an object in C++ can be represented like an automaton,
and methods of a C++ object can be represented like an automaton,
so computer programming thinking is like constructing many
interconnected automaton and is like constructing Petri Nets,
and my second question is: Is computer programming a science ?
i think computer programming can be made a science by making those many
interconnected automaton or those Petri Nets more efficient.
This is how i think computer programming can be described.
 
 
 
Thank you,
Amine Moulay Ramdane.
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