Re: [Boost-users] Boost-users Digest, Vol 2679, Issue 1

Subject: Re: [Boost-users] Boost-users Digest, Vol 2679, Issue 1
From: Shah, Gaurav N (gaurav.n.shah_at_[hidden])
Date: 2011-04-01 04:09:01

Thanks Andreas Wehrmann.
if worked after including boost/function.hpp.

I am still wondering what changes boost has made while moving from 1.41 to 1.44 that has made users to explicitly include "function.hpp" This code was compiling with 1.41 without including boost/function.hpp

Thank You,
Gaurav

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Today's Topics:

   1. Re: [boost::mutex] Do they block or wait? (Ovanes Markarian)
   2. Re: [Lambda] nitty gritty detail...? (Robert Jones)
   3. Re: [Lambda] nitty gritty detail...? (Steven Watanabe)
   4. VS2010+boost 1.44 - error in move.hpp (archie14)
   5. [boost] [program options] Potential bug in parsing arguments
      where one is suffix of the other ? (Sanjit Jhala)
   6. [MPL] no invoke<T>? (Noah Roberts)
   7. Re: Problem with gcc/4.5.0-g++and boost::function
      (Andreas Wehrmann)


----------------------------------------------------------------------

Message: 1
Date: Thu, 31 Mar 2011 20:21:29 +0200
From: Ovanes Markarian <om_boost_at_[hidden]>
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [boost::mutex] Do they block or wait?
Message-ID:
	<AANLkTim_=MZAk0WwoerK7-TCRAGpN0Gdgcr+DDV5uhOA_at_[hidden]>
Content-Type: text/plain; charset="iso-8859-1"

On Thu, Mar 31, 2011 at 7:49 PM, Steven Watanabe <watanabesj_at_[hidden]>wrote:

> AMDG
>
>
> On 03/31/2011 09:55 AM, Panagiotis Foteinos wrote:
>
>> I looked into the documentation, but it is still unclear to me.
>>
>> [...]
>
> boost's locking mechanism
>> blocking or spinning?
>>
>>
> It's an implementation detail.  You realize that the
> two aren't necessarily mutually exclusive?  Anyway,
> Boost.Thread does block on an Event.  A spin-lock
> only makes sense on a multi-core system.
>
> In Christ,
> Steven Watanabe
>

As Steven pointed out it is an implementation detail and these two concepts
might be used together  (primarily for optimization). Switching to kernel
mode (e.g. dealing with kernel objects like event, mutex, semaphore through
system calls) is a very time costly operation, therefore some libs provide
spinning optimizations, which do spinning (for some few cpu cycles) and if
they are still unable to acquire a lock, they make a system call which
changes into the kernel mode and finally puts the thread into the blocked
state if the object is still not available (signaled, unlocked etc). But
even so it is not black and white in the concurrency world. :( Some would
like to achieve speed through such an optimization others would like to get
rid of such an optimization. A good example might be an embedded app running
on a battery driven HW, where energy plays a major role. Here wasting CPU
cycles for speed optimization might not be a good idea... But anyway that
should be separately evaluated.


With Kind Regards,
Ovanes
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Message: 2
Date: Thu, 31 Mar 2011 19:27:30 +0100
From: Robert Jones <robertgbjones_at_[hidden]>
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Lambda] nitty gritty detail...?
Message-ID:
	<AANLkTinfsOJmqrWBP16+7s2c+YufKcW3GwcHapxttLqq_at_[hidden]>
Content-Type: text/plain; charset="iso-8859-1"

On Thu, Mar 31, 2011 at 4:47 PM, Steven Watanabe <watanabesj_at_[hidden]>wrote:

> AMDG
>
>
> On 03/31/2011 08:29 AM, Robert Jones wrote:
>
>> From Bjorn Karlsson's book, P297...
>>>
>>
>> int i;
>> int value = 12;
>> var(i) = ( if_then_else_return( _1>=10, constant(10),_1) )(value);
>>
>> Why does the assignment LHS need to be wrapped in var()?
>>
>>
> Because operator= must be a member function.
>
>
Nope, still not getting it! Stop me when I err...

if_then_else_return(...) defines a unary functor
it_then_else_return(...)( value) evaluates that functor, and returns what?

Some type of integer I think? So doesn't the assignment simply perform
assignment of an integer, by copy? And that doesn't need operator= to
a member of anything?

Thanks

- R.
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Message: 3
Date: Thu, 31 Mar 2011 11:38:33 -0700
From: Steven Watanabe <watanabesj_at_[hidden]>
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] [Lambda] nitty gritty detail...?
Message-ID: <4D94CA29.9060307_at_[hidden]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

AMDG

On 03/31/2011 11:27 AM, Robert Jones wrote:
> On Thu, Mar 31, 2011 at 4:47 PM, Steven Watanabe<watanabesj_at_[hidden]>wrote:
>>
>> On 03/31/2011 08:29 AM, Robert Jones wrote:
>>
>>>  From Bjorn Karlsson's book, P297...
>>>>
>>>
>>> int i;
>>> int value = 12;
>>> var(i) = ( if_then_else_return( _1>=10, constant(10),_1) )(value);
>>>
>>> Why does the assignment LHS need to be wrapped in var()?
>>>
>>>
>> Because operator= must be a member function.
>>
>>
> Nope, still not getting it! Stop me when I err...
>
> if_then_else_return(...) defines a unary functor
> it_then_else_return(...)( value) evaluates that functor, and returns what?
>
> Some type of integer I think?

Yes.

> So doesn't the assignment simply perform
> assignment of an integer, by copy? And that doesn't need operator= to
> a member of anything?
>

Oh, I see.  As written, the code doesn't make much
sense, so my mind automatically translated it into

(var(i) = if_then_else_return( _1>=10, constant(10),_1) )(value);

In Christ,
Steven Watanabe


------------------------------

Message: 4
Date: Thu, 31 Mar 2011 22:56:11 +0000 (UTC)
From: archie14 <admin_at_[hidden]>
To: boost-users_at_[hidden]
Subject: [Boost-users] VS2010+boost 1.44 - error in move.hpp
Message-ID: <loom.20110401T005027-111_at_[hidden]>
Content-Type: text/plain; charset=us-ascii

While compiling the project in VS2010 previously built without errors in 
VS2008 I am getting following error:

c:\libraries\boost\boost_1_44_0\boost\interprocess\detail\move.hpp(342): error 
C2440: 'return' : cannot convert from 'boost::interprocess::file_mapping' 
to 'boost::interprocess::file_mapping &&'
         You cannot bind an lvalue to an rvalue reference
         c:\libraries\boost\boost_1_44_0\boost\interprocess\file_mapping.hpp
(62) : see reference to function template 
instantiation 'boost::interprocess::file_mapping 
&&boost::interprocess::move<boost::interprocess::file_mapping&>(T)' being 
compiled
          with
         [
             T=boost::interprocess::file_mapping &
         ]


I tried to search the forum for the reports on this error and did not find 
anything.

I'll appreciate any help in this matter.



------------------------------

Message: 5
Date: Thu, 31 Mar 2011 16:16:25 -0700
From: Sanjit Jhala <sjhalaz_at_[hidden]>
To: boost-users_at_[hidden]
Subject: [Boost-users] [boost] [program options] Potential bug in
	parsing arguments where one is suffix of the other ?
Message-ID:
	<AANLkTi=bEJWMhNj-wO-9O6SjHORiGkr0xn75pKeJOU4=@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

Hi,

I have the following code (modified from example/first.cpp):

*#include <boost/program_options.hpp>*
*#include <string>*
*#include <vector>*
*#include <iostream>*
*
*
*namespace po = boost::program_options;*
*
*
*using namespace std;*
*
*
*typedef vector<string> Strings;*
*
*
*// A helper function to simplify the main part.*
*template<class T>*
*ostream& operator<<(ostream& os, const vector<T>& v)*
*{*
*  copy(v.begin(), v.end(), ostream_iterator<T>(cout, " "));*
*  return os; *
*}*
*
*
*
*
*int main(int argc, char *argv[]) {*
*
*
*  po::options_description cmdline_desc("Usage: %s [Options]
[args]\nOptions");*
*  cmdline_desc.add_options()*
*      ("str", po::value< string >(), "a string arg")*
*      ("strs", po::value< Strings >(), "a list of strings")*
*      ("foo", po::value< string >(), "a string arg")*
*      ("bar", po::value< Strings >(), "a list of strings")*
*      ;   *
*
*
*  po::variables_map vm; *
*  po::store(po::parse_command_line(argc, argv, cmdline_desc), vm);*
*  po::notify(vm);*
*
*
*  if (vm.count("str"))*
*    cout << "Got str arg=" << vm["str"].as< string >() << "\n";*
*  if (vm.count("strs"))*
*    cout << "Got strs arg=" << vm["strs"].as< Strings >() << "\n";*
*  if (vm.count("foo"))*
*    cout << "Got foo arg=" << vm["foo"].as< string >() << "\n";*
*  if (vm.count("bar"))*
*    cout << "Got bar arg=" << vm["bar"].as< Strings >() << "\n";*
*}*
*
*
When I run the program I see:
*./po_test --str "a string" --strs "a, vector, of, strings" --foo "a foo"
--bar "a, bar"*
*Got strs arg=a string a, vector, of, strings *
*Got foo arg=a foo*
*Got bar arg=a, bar *

It appears the parser is getting confused between the "str" and the "strs".
It doesn't seem to be related to ambiguity in handling vectors since the
"foo" and "bar" arguments are fine. I see this problem on 32-bit CentOS and
Ubuntu machines, but not on 64-bit. I am running Boost 1.43 and from
the /usr/local/include/boost/program_options/version.hpp:
#define BOOST_PROGRAM_OPTIONS_VERSION_HPP_VP_2004_04_05
#define BOOST_PROGRAM_OPTIONS_VERSION 2

Is this a bug or a expected behaviour?

-Sanjit
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Message: 6
Date: Thu, 31 Mar 2011 16:32:13 -0700
From: Noah Roberts <roberts.noah_at_[hidden]>
To: boost-users_at_[hidden]
Subject: [Boost-users] [MPL] no invoke<T>?
Message-ID: <in32tm$6u3$1_at_[hidden]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

I had to write an invoke metafunction because I couldn't seem to find 
one that looked like it was what I needed:

template < typename MF > struct invoke { typedef typename MF::type type; };

I've looked through the documentation TOC: 
http://www.boost.org/doc/libs/1_42_0/libs/mpl/doc/refmanual/refmanual_toc.html


Is there something I'm missing?



------------------------------

Message: 7
Date: Fri, 01 Apr 2011 08:04:18 +0200
From: Andreas Wehrmann <a.wehrmann_at_[hidden]>
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] Problem with gcc/4.5.0-g++and
	boost::function
Message-ID: <4D956AE2.4040808_at_[hidden]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 03/31/2011 06:42 PM, Steven Watanabe wrote:
> AMDG
>
> On 03/31/2011 09:27 AM, Shah, Gaurav N wrote:
>> I have legacy code in my library using boost::function. This works 
>> fine if I am using gcc/4.2.2-g++ and BOOST/1.41.  But if I switch 
>> myself to using gcc/4.5.0-g++ and BOOST/1.44 I get below ERROR:
>> I do not see anything wrong with code.
>>
>> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:51: 
>> error: 'function' in namespace 'boost' does not name a type
>> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:58: 
>> error: ISO C++ forbids declaration of 'parameter' with no type
>> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:66: 
>> error: expected ',' or '...' before '<' token
>> ../../../../../../marketdata/IMDMXP/server/wombat/management.cpp:126:10: 
>> error: prototype for 'void datasource::management::stop(const 
>> std::string&, const boost::function<void()>&)' does not match any in 
>> class 'datasource::management'
>> /export/home/a_besnad/Perforce/eq-thebeast-build-linux-Beast_8.08/TheBeast/marketdata/IMDMXP/server/wombat/management.hpp:69:14: 
>> error: candidate is: void datasource::management::stop(const 
>> std::string&, int)
>> make[6]: *** [management.lo] Error 1
>> make[6]: *** Waiting for unfinished jobs....
>>
>>
>>
>> Code lines throw ERROR:
>>
>> 68           */
>> 69         void stop(const std::string&  topic, const 
>> boost::function<  void (void)>&  action);
>> 70
>>
>> Thanks for help in advance.
>>
>
> Have you verified that boost/function.hpp
> is #included?
>
> In Christ,
> Steven Watanabe
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users


This is the first thing I would check, since the compiler has become 
stricter, meaning
indirect inclusions won't work anymore.
I ran across the same problem when upgrading from 4.2.x to 4.4.x and 
4.5.x respectively.

Regards,
Andreas

-- 
Dipl.-Ing. (FH) Andreas Wehrmann
Software Development
--------------------------------------------------------------
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