cppcms-users

[Cppcms-users] boost.locale and date formatting

[augustin <aug...@ov...>]

(second try to send this to the list)

Hello,

Speaking of boost(er).locale, I am having problems formatting dates.

I tried the simple example from here:
http://cppcms.sourceforge.net/boost_locale/html/formatting_and_parsing.html

#include <iostream>
#include <sstream>
#include <boost/locale.hpp>

using std::cout;
using std::endl;
using namespace boost::locale;

int main() {
        double now=time(0);
        cout << "Today is "<< as::date << now << " and tommorrow is " << 
now+24*3600 << endl;
        cout << "Current time is "<< as::time << now << endl;
        cout << "The current weekday is "<< as::ftime("%A") << now << endl;
}

g++ main.cpp -o run.main -lboost_locale

and the output is:

Today is 1.30439e+09 and tommorrow is 1.30448e+09
Current time is 1.30439e+09
The current weekday is 1.30439e+09

I tried with booster.locale that comes with cppcms, and I downloaded from svn 
and compiled the very latest boost.locale. I get the same result with both.

I'm sure I am missing something simple. 
Probably, I need to set the locale first, but it's not clear to me how to do 
it.

Also, a grip I have with most/all boost libraries, is that one never knows 
what option to pass to the linker:
http://stackoverflow.com/questions/3467153/is-there-an-intelligent-way-to-know-
the-name-of-the-library-to-link-to-at-compile
Is this platform/compiler dependent? Can't this kind of thing be documented?
Anyway, in this case, I found it was -lboost_locale.

For boost.locale, more, fully working, compilable examples would help.

-

Most boost libraries documentation are written for very experienced C++ 
developers. From a newbie perspective, I find most documentation very obtuse. I 
checked boost.date_time for a long while, and still couldn't understand enough  
to actually make use of it. I still have much to learn before I can understand 
a lot of the boost documentation.

-

Generally speaking, within the context of a cppcms application, what is the 
best/recommended way to format dates, times and such?
Basically, I have a unix timestamp, and I want to output it in human readable 
form, both in the UTC and locale timezone.


Thanks,

Augustin.




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Re: [Cppcms-users] boost.locale and date formatting

[Artyom <art...@ya...>]

> From: augustin <aug...@ov...>
> 
> (second try to send this to the list)
> 
> Hello,
> 
> Speaking of  boost(er).locale, I am having problems formatting dates.
> 
> I tried the  simple example from  here:
> [...]


See: http://thread.gmane.org/gmane.comp.lib.boost.devel/218008

> I'm sure I am missing something simple. 
> Probably, I need to set the locale first, but it's not clear to me how to do 
> it.

See section about locale generation.

> 
> Also, a grip I have with most/all boost libraries, is that one  never knows 
> what option to pass to the  linker:
> 
http://stackoverflow.com/questions/3467153/is-there-an-intelligent-way-to-know-
> the-name-of-the-library-to-link-to-at-compile
> Is  this platform/compiler dependent? Can't this kind of thing be  documented?
> Anyway, in this case, I found it was -lboost_locale.
> 

This is something Boost general not related
to Boost.Locale specifically.

> For  boost.locale, more, fully working, compilable examples would  help.
> 

Take a look on libs/locale/examples
with full code to see what you miss.

> -
> 
> Most boost libraries documentation are written for very  experienced C++ 
> developers. From a newbie perspective, I find most  documentation very obtuse. 
>I 
>
> checked boost.date_time for a long while, and  still couldn't understand 
>enough  
>
> to actually make use of it. I still  have much to learn before I can understand 
>
> a lot of the boost  documentation.
> 
> -


This specific "problem" would be added to FAQ.

> 
> Generally speaking, within the context of a  cppcms application, what is the 
> best/recommended way to format dates, times  and such?
> Basically, I have a unix timestamp, and I want to output it in  human readable 

> form, both in the UTC and locale  timezone.
> 

Read the tutorial there are an examples how to make UTC, local timezone 
(default)
or custom time zone output (there is a manipulator for this purpose and 
formatting
flags).

Also the way you want to display dates is application specific and dependent
on use case.

Best,
  Artyom

Re: [Cppcms-users] C++ locale and boost.locale

[augustin <aug...@ov...>]

On Wednesday 04 May 2011 03:35:35 pm Artyom wrote:
> See: http://thread.gmane.org/gmane.comp.lib.boost.devel/218008
> [...]
> See section about locale generation.

Thanks. The discussion thread you link to, and your mention prompted me to do 
some further research and I finally figured out that I was missing yet another 
whole chapter of this very complex, yet fascinating language (C++).
I hadn't grasped how the concept of locale was deeply embedded within the 
language itself:
http://www.cplusplus.com/reference/std/locale/ 
http://stdcxx.apache.org/doc/stdlibug/VII.html 
chapter 22 of c++0x,
chapter 27 of c++03.

With only 400+ hours of experience with C++, I still count as a very beginner. 
It's been 400 hours worth of shocks at discovering how many facets there are 
to the language, and how many ancillary skills (compiling, linking, gnu tools, 
Makefile, cmake, etc.)  and libraries (std, STL, std::locale, boost, cppcms, 
cppdb and others I am using...) I have yet to master to become, hopefully one 
day, a decent C++ programmer. 

In the boost.locale documentation, as part of the introduction, you ought to 
make a list of assumed knowledge, with some links like those I provided above, 
to redirect people like me to background information.

I'm going to be reading about all this now...

> http://stackoverflow.com/questions/3467153/is-there-an-intelligent-way-to-k
> now-
> 
> > the-name-of-the-library-to-link-to-at-compile
> > Is  this platform/compiler dependent? Can't this kind of thing be 
> > documented? Anyway, in this case, I found it was -lboost_locale.
> 
> This is something Boost general not related
> to Boost.Locale specifically.

Yes, but it affects every single boost library, including yours. Maybe you can 
add such necessary information to the boost.locale documentation.


> Take a look on libs/locale/examples
> with full code to see what you miss.

Oh, yes, I did miss that! Very cool, thanks. 

Thanks again for your constant support. Your answers were very helpful in 
pointing me in the right direction. I have much study to do, now... ;)

Btw, since I have a svn checkout (ever considered using git? Yet another thing 
I need to learn: how to link a local git working directory to a svn upstream 
source. I know there are tutorials about it, that I can find easily... there is 
so much to do and to learn!)... I was saying: since I checked out boost.locale 
from svn, let me know if you'd like me to prepare a patch for the 
documentation.... (I am still waiting for your review of my form.h patch, 
though...).


Blessings,

Augustin.







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Re: [Cppcms-users] C++ locale and boost.locale

[augustin <aug...@ov...>]

On Wednesday 04 May 2011 08:37:33 pm augustin wrote:
> In the boost.locale documentation, as part of the introduction, you ought
>  to make a list of assumed knowledge, with some links like those I provided
>  above, to redirect people like me to background information.

Oops. You actually already do:
http://cppcms.sourceforge.net/boost_locale/html/std_locales.html 
I read it too quickly the first time and didn't understand what I was reading.
It's slowly sinking in...

Sorry for the noise.

Augustin.




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Re: [Cppcms-users] C++ locale and boost.locale

[Artyom <art...@ya...>]

> > > Is  this  platform/compiler dependent? Can't this kind of thing be 
> > >  documented? Anyway, in this case, I found it was -lboost_locale.
> > 
> > This is something Boost general not related
> > to Boost.Locale  specifically.
> 
> Yes, but it affects every single boost library, including  yours. Maybe you can 
>
> add such necessary information to the boost.locale  documentation.
> 

It is not something trivial especially when you use MSVC with its
endless incompatible build variants.

See:

  http://www.boost.org/doc/libs/1_46_1/more/getting_started/unix-variants.html
  http://www.boost.org/doc/libs/1_46_1/more/getting_started/windows.html


> ever considered using git?

Subversion has a huge advantage of working
over https behind firewalls and in various
even untrusted networks. So if you work
from University network or just some public
network there is no replacement for https
support.

GIT does not allow to perform commits over
https protocol like SVN.

> (I am still waiting for your review of my  form.h patch, 
> though...).

I'm sorry, you are right.

Was too damn busy, I'll try to get to it this week.
Drop me a mail if I forget once again.

Regards, 
  Artyom

Re: [Cppcms-users] C++ locale and boost.locale

[augustin <aug...@ov...>]

On Wednesday 04 May 2011 09:29:39 pm Artyom wrote:
>  http://www.boost.org/doc/libs/1_46_1/more/getting_started/unix-
variants.html
> http://www.boost.org/doc/libs/1_46_1/more/getting_started/windows.html

Ha! Even by reading the official boost documentation page about linking, I 
wouldn't have guessed what linker option to chose. 

For Linux/g++, at least, it wouldn't hurt mentioning the -lboost_locale in the 
docs.

> Was too damn busy, I'll try to get to it this week.
> Drop me a mail if I forget once again.

There's no actual hurry as far as I am concerned, but something just came up 
today and I may have to travel to Europe for two weeks later this month, so I 
won't be available then, if I do go.



BTW, thanks to your help, I got the missing piece, so that I finally managed to 
do what I wanted to do:

#include <sstream>
#include <boost/locale.hpp>

std::string timestamp_to_string(time_t const& tt) {
        using namespace boost::locale;
        generator gen;
        std::locale::global(gen("en_US.UTF-8"));
        std::stringstream ss;
        ss.imbue(std::locale());
        ss << as::date << tt << " ";
        ss << as::time << tt << std::endl;
        std::string r = "";
        getline(ss, r);
        return r;
}

It took me 10-20 hours to research, read and understand enough to come up with 
the seemingly simple piece of code above. :-/ 

I use it to format unix timestamps before pushing it to my 
cppcms::base_content object.

I don't know if it's the right approach, but it works...



Augustin.

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Re: [Cppcms-users] C++ locale and boost.locale

[Artyom <art...@ya...>]

> 
> BTW, thanks to your help, I got the  missing piece, so that I finally managed 
>to 
>
> do what I wanted to  do:
> 
> #include <sstream>
> #include  <boost/locale.hpp>
> 
> std::string timestamp_to_string(time_t  const& tt) {
>         using namespace  boost::locale;
>         generator gen;
>          std::locale::global(gen("en_US.UTF-8"));
>          std::stringstream ss;
>          ss.imbue(std::locale());
>         ss << as::date  << tt << " ";
>         ss << as::time  << tt << std::endl;
>         std::string r =  "";
>         getline(ss, r);
>          return r;
> }
> 

Few points:

> timestamp_to_string(time_t  const& tt) 

It is better to write

   timestamp_to_string(time_t tt) 

As time_t is integral type and it is better
to pass it by value.

>         using namespace  boost::locale;
>         generator gen;
>          std::locale::global(gen("en_US.UTF-8"));
>          ss.imbue(std::locale());


Is very inefficient as locale generation is very
heavy procedure.

In CppCMS context you have this member function:

http://cppcms.sourceforge.net/cppcms_ref_v0_99/classcppcms_1_1http_1_1context.html#39fde738210daf84deee691f45260e5b


So basically inside cppcms::application based class just write

  std::locale loc = context().locale();

or

  std::locale loc = context().locale("en_US.UTF-8");

It returns the locale defined in configuration file for you
and it would cache the locale automatically for future use.

>          std::locale::global(gen("en_US.UTF-8"));
>          ss.imbue(std::locale());


Even if you use it, it is better to write

    ss.imbue(gen("en_US.UTF-8"));

And not set global locale and then create a locale
instance from global one.

>         ss << as::date  << tt << " ";
>         ss << as::time  << tt << std::endl;

It is better to write

   ss << as::datetime << tt;

>         std::string r =  "";

r is empty by default, no need r="";

>         getline(ss, r);
>          return r;

It is better to call

   return ss.str()

Of course without "<<std::endl"




> It took me 10-20 hours to research, read and  understand enough to come up with 
>
> the seemingly simple piece of code above.  :-/ 
> 
> I use it to format unix timestamps before pushing it to my 
> cppcms::base_content object.
> 
> I don't know if it's the right approach,  but it works...
> 

It is much simpler, you have filers namespace

  http://cppcms.sourceforge.net/cppcms_ref_v0_99/namespacecppcms_1_1filters.html

So just write in the template


   <% tt | datetime %> 

Or even with more fine grained control

   <% tt | strftime("%Y-%m-%d %H:%M:%S %Z") %> 


where tt is just time_t in your context :-)

> 
> 
> Augustin.


Best,
  Artyom

Re: [Cppcms-users] C++ locale and boost.locale

[augustin <aug...@ov...>]

On Thursday 05 May 2011 12:52:44 am Artyom wrote:
> >         getline(ss, r);
> >          return r;
>
> It is better to call
> 
>    return ss.str()

Oops! This one is very embarrassing given the time I wasted trying to figure 
out a simple way to extract the string from the stream!

Thank you very much for all your comments on my code. They're duly noted. I 
appreciate it.

>  http://cppcms.sourceforge.net/cppcms_ref_v0_99/namespacecppcms_1_1filters.
> html
> 
> So just write in the template
> 
> 
>    <% tt | datetime %>
> 
> Or even with more fine grained control
> 
>    <% tt | strftime("%Y-%m-%d %H:%M:%S %Z") %>
> 
> 
> where tt is just time_t in your context :-)

Ah, yes! You just answered my earlier question about locales in a cppcms 
context. This is actually what I meant. I knew my approach didn't feel right.

It works as it should, now.

Thanks again,

augustin.



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