Saturday, July 6, 2019

Digest for comp.lang.c++@googlegroups.com - 16 updates in 7 topics

Szyk Cech <szykcech@spoko.pl>: Jul 06 05:54PM +0200

Hi
I want to write nice join template function. In order to work with
different containers and with wide and narrow strings it must be template.
Now I have some thing like this:
 
 
/**
* @brief Joins strings in container.
* @param aStringList an container wiht strings.
* @param aDelimiter string witch joins strings in container.
* @result String joined with delimiter.
*/
 
template<template<typename> typename tContainer, typename tString>
tString gJoin(const tContainer<tString>& aStringList, const tString&
aDelimiter)
{
tString lResult;
for(tString lPart : aStringList)
{
if(lResult.size() > 0)
lResult += aDelimiter;
lResult += lPart;
}
 
return lResult;
}
 
But it not works. My g++ is:
gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)
 
I learn that it should work from:
https://en.cppreference.com/w/cpp/language/template_parameters
 
Error is like this:
 
/home/szyk/!-EnergoKod/!-Libs/EnergoKodTools2/Tests/Src/StringTest.cpp:
In member function 'void StringTest::test7()':
/home/szyk/!-EnergoKod/!-Libs/EnergoKodTools2/Tests/Src/StringTest.cpp:126:76:
error: no matching function for call to
'gJoin<std::vector<std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> >,
std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>,
std::allocator<char> > > >,
std::__cxx11::string>(std::vector<std::__cxx11::basic_string<char> >&,
std::__cxx11::basic_string<char>)'
std::string lTest1A(gJoin<vector<string>, string>(lVector1,
string(" ")));

^
In file included from
/home/szyk/!-EnergoKod/!-Libs/EnergoKodTools2/Tests/Src/StringTest.cpp:4:0:
/home/szyk/!-EnergoKod/!-Libs/EnergoKodTools2/Include/EnergoKodTools2/Strings.h:148:9:
note: candidate: template<template<class> class tContainer, class
tString> tString ekt2::gJoin(const tContainer<tString>&, const tString&)
tString gJoin(const tContainer<tString>& aStringList, const tString&
aDelimiter)
^~~~~
/home/szyk/!-EnergoKod/!-Libs/EnergoKodTools2/Include/EnergoKodTools2/Strings.h:148:9:
note: template argument deduction/substitution failed:
Tests/CMakeFiles/EnergoKodTools2Test.dir/build.make:158: recipe for
target 'Tests/CMakeFiles/EnergoKodTools2Test.dir/Src/StringTest.cpp.o'
failed
make[2]: ***
[Tests/CMakeFiles/EnergoKodTools2Test.dir/Src/StringTest.cpp.o] Error 1
make[1]: *** [Tests/CMakeFiles/EnergoKodTools2Test.dir/all] Error 2
make: *** [all] Error 2
CMakeFiles/Makefile2:122: recipe for target
'Tests/CMakeFiles/EnergoKodTools2Test.dir/all' failed
Makefile:129: recipe for target 'all' failed
17:45:51: Proces "/usr/bin/cmake" zakończył się kodem wyjściowym 2.
Błąd budowania / instalowania projektu EnergoKodTools2 (zestaw narzędzi:
Desktop Qt 5.12.3 GCC 64bit2)
Podczas wykonywania kroku "Wersja CMake"
 
 
please help me,
best regards,
and thanks in advance
Szyk Cech
Szyk Cech <szykcech@spoko.pl>: Jul 06 07:59PM +0200

Thanks a lot!!!
 
I improve my code with your help! And it pass all my tests now.
 
Problem was that I rely on Qt Creator buildin C++ parser (based on CLang
compiler libraries). And how ever I have compile able and valid template
function code, I try crazy calls of this function, because I believe in
parser. Apparently it does not recognize C++17 fully. Not sure, but
maybe it is not upgraded to newest version (but I have newest Qt Creator).
 
 
Final version of my gJoin() template function looks like:
 
/**
* @brief Joins wide and narrow strings in any container.
* @param aStringList an container with strings.
* @param aDelimiter string witch joins strings in container.
* @result String joined with delimiter.
* @warning Don't call this function with different string types
* as containter template parameter and as delimiter - if you do this
you will
* get compile error.
*/
 
template<template<typename> typename tContainer, typename tString>
tString gJoin(const tContainer<tString>& aStringList, const tString&
aDelimiter)
{
tString lResult;
 
for(tString lPart : aStringList)
{
if(not lResult.empty())
lResult += aDelimiter;
lResult += lPart;
}
 
return lResult;
}
bitrex <user@example.net>: Jul 06 01:39PM -0400

I have two Thread subclasses in the openFrameworks API that receive data
from a third thread via a lock-free FIFO, e.g:
 
<https://openframeworks.cc/documentation/utils/ofThreadChannel/>
 
process it a bit and then transmit it out to their own independent
hardware serial ports.
 
I am looking for a suggestion on what C++1x technique or library I could
use to allow synchronizing the output data transmission routine timing
to a thread-safe master reference clock, but allow the data input to the
threads to remain asynchronous.
bitrex <user@example.net>: Jul 06 01:43PM -0400

On 7/6/19 1:39 PM, bitrex wrote:
> use to allow synchronizing the output data transmission routine timing
> to a thread-safe master reference clock, but allow the data input to the
> threads to remain asynchronous.
 
I guess since the threads are already getting their xmit data via a FIFO
of that type they could also receive timing clock data the same way...
James Kuyper <jameskuyper@alumni.caltech.edu>: Jul 06 06:59AM -0700

On Friday, July 5, 2019 at 7:23:03 PM UTC-4, G G wrote:
> On Friday, July 5, 2019 at 7:20:02 PM UTC-4, G G wrote:
> > On Friday, July 5, 2019 at 7:10:24 PM UTC-4, Öö Tiib wrote:
...
 
> > yes
 
> i stop at line 34. preprocessor macros
 
> are you say those preprocessor statement would not work in C++?
 
The #define itself works the same way in both languages. However, which
definition is given to that macro depends upon whether __STDC__ is
#defined, and also upon how it is defined. The double underscores at
the beginning mean that__STDC__ is a reserved identifier for C++, but
the C++ standard specifies nothing about what value it has. So yes, the
wrong definition for that prototype might be chosen.
 
More directly to the point, those preprocessor directives (the two
#defines for PROTOTYPE, as well at the #if, #else, and
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