Monday, May 17, 2021

Digest for comp.lang.c++@googlegroups.com - 8 updates in 2 topics

"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: May 17 04:05PM -0700

I don't think this should work at all! It should segfault.
_______________________________
#include <iostream>
#include <algorithm>
#include <string>
#include <set>
 
 
struct person
{
person(std::string const& name, unsigned long id)
: m_name(name), m_id(id)
{
std::cout << "(" << this << ")->person::person(" << name << ",
" << id << ")\n";
}
 
~person()
{
std::cout << "(" << this << ")->person::~person(" << m_name <<
", " << m_id << ")\n";
}
 
void display() const
{
std::cout << "(" << this << ")->person::display(" << m_name <<
", " << m_id << ")\n";
}
 
std::string m_name;
unsigned long m_id;
};
 
 
struct database
{
struct key_id
{
using is_transparent = void; // Humm...
 
bool operator() (person const& p0, person const& p1) const
{
return p0.m_id < p1.m_id;
}
 
bool operator() (std::string const name, person const& p) const
{
return name < p.m_name;
}
 
bool operator() (person const& p, std::string const name) const
{
return p.m_name < name;
}
 
bool operator() (unsigned long id, person const& p) const
{
return id < p.m_id;
}
 
bool operator() (person const& p, unsigned long id) const
{
return p.m_id < id;
}
};
 
typedef std::set<person, key_id> set_t;
 
void add_entry(person const& p0)
{
m_set.insert(p0);
}
 
set_t::iterator const& search_id(unsigned long id) const
{
return m_set.find(id);
}
 
set_t::iterator const& search_id(std::string const& name) const
{
return m_set.find(name);
}
 
void display() const
{
std::cout << "\n(" << this << ")->database::display()\n";
std::cout << "_____________________________________\n";
std::for_each(m_set.begin(), m_set.end(), [](person const& p)
{
p.display();
});
std::cout << "_____________________________________\n\n";
}
 
set_t m_set;
};
 
 
int main()
{
{
database db;
 
db.add_entry(person("Chris", 42));
db.add_entry(person("Lisa", 23));
db.add_entry(person("Randall", 37));
 
std::cout << "_____________________________________\n\n";
 
{
database::set_t::iterator result = db.search_id(37);
if (result != db.m_set.end())
{
std::cout << "FOUND 37!\n";
(*result).display();
}
}
 
{
database::set_t::iterator result = db.search_id(137);
if (result == db.m_set.end()) std::cout << "137 NOT
FOUND!\n\n";
}
 
{
database::set_t::iterator result = db.search_id("Lisa");
if (result != db.m_set.end())
{
std::cout << "FOUND ""Lisa""\n";
(*result).display();
}
}
 
db.display();
}
 
return 0;
}
_______________________________
"Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: May 17 04:11PM -0700

On 5/17/2021 4:05 PM, Chris M. Thomasson wrote:
> I don't think this should work at all! It should segfault.
> _______________________________
[snip buggy code that seems to work in MSVC]
> _______________________________
 
Now, this version should go ahead and work? It seems to.
_________________________________
#include <iostream>
#include <algorithm>
#include <string>
#include <set>
 
 
struct person
{
person(std::string const& name, unsigned long id)
: m_name(name), m_id(id)
{
std::cout << "(" << this << ")->person::person(" << name << ",
" << id << ")\n";
}
 
~person()
{
std::cout << "(" << this << ")->person::~person(" << m_name <<
", " << m_id << ")\n";
}
 
void display() const
{
std::cout << "(" << this << ")->person::display(" << m_name <<
", " << m_id << ")\n";
}
 
std::string m_name;
unsigned long m_id;
};
 
 
struct database
{
struct key_id
{
using is_transparent = void; // Humm...
 
bool operator() (person const& p0, person const& p1) const
{
return p0.m_id < p1.m_id;
}
 
bool operator() (std::string const name, person const& p) const
{
return name < p.m_name;
}
 
bool operator() (person const& p, std::string const name) const
{
return p.m_name < name;
}
 
bool operator() (unsigned long id, person const& p) const
{
return id < p.m_id;
}
 
bool operator() (person const& p, unsigned long id) const
{
return p.m_id < id;
}
};
 
typedef std::set<person, key_id> set_t;
 
void add_entry(person const& p0)
{
m_set.insert(p0);
}
 
set_t::iterator const search_id(unsigned long id) const
{
return m_set.find(id);
}
 
set_t::iterator const search_id(std::string const& name) const
{
return m_set.find(name);
}
 
void display() const
{
std::cout << "\n(" << this << ")->database::display()\n";
std::cout << "_____________________________________\n";
std::for_each(m_set.begin(), m_set.end(), [](person const& p)
{
p.display();
});
std::cout << "_____________________________________\n\n";
}
 
set_t m_set;
};
 
 
int main()
{
{
database db;
 
db.add_entry(person("Chris", 42));
db.add_entry(person("Lisa", 23));
db.add_entry(person("Randall", 37));
 
std::cout << "_____________________________________\n\n";
 
{
database::set_t::iterator const& result = db.search_id(37);
if (result != db.m_set.end())
{
std::cout << "FOUND 37!\n";
(*result).display();
}
}
 
{
database::set_t::iterator const& result = db.search_id(137);
if (result == db.m_set.end()) std::cout << "137 NOT
FOUND!\n\n";
}
 
{
database::set_t::iterator const& result = db.search_id("Lisa");
if (result != db.m_set.end())
{
std::cout << "FOUND ""Lisa""\n";
(*result).display();
}
}
 
db.display();
}
 
return 0;
}
_________________________________
MrSpook_qg11H@ihwz2zmflqtcalb.gov.uk: May 17 04:06PM

On Mon, 17 May 2021 17:58:16 +0200
>> or
>> pure virtual func();
 
>It's the same for me but not for compulsive personalities.
 
Oh ok. Well why use words at all then? Why not have something like
 
@@func() = 0;
 
C++ could end up like the explosion in an ascii factory that is objective-C.
 
>> it exists is to make life easier. Having moronic syntax has the opposite
>effect.
 
>That's not a practical reason.
 
A stupid response.
 
>> static int i = 123;
>> };
 
>There is a good reason because there's only one definition of i.
 
Ok, you don't understand the concept of initialisation. Thanks for clearing
that up.
 
>> All these "tiny" problems add up.
 
>No, they stand side by side.
 
And with attitudes like that C++ will continue to be shunned by new
generations of programmers.
Bonita Montero <Bonita.Montero@gmail.com>: May 17 06:21PM +0200


>> It's the same for me but not for compulsive personalities.
 
> Oh ok. Well why use words at all then? Why not have something like
> @@func() = 0;
 
That's a matter of habituation.
 
>> effect.
 
>> That's not a practical reason.
 
> A stupid response.
 
No, I asked for practical reasons and not metaphors.
 
 
>> There is a good reason because there's only one definition of i.
 
> Ok, you don't understand the concept of initialisation. Thanks for clearing
> that up.
 
There is a good reason for this to be not legal: the one-definition
-rule. If you want it the way which is up to your taste define the
variable inline and compile the code with C++17.
 
 
>> No, they stand side by side.
 
> And with attitudes like that C++ will continue to be shunned by new
> generations of programmers.
 
You didn't name any real problems which coudn't be solved in a blink
of an eye.
Juha Nieminen <nospam@thanks.invalid>: May 17 04:36PM

>>> the difference between their backsides and a type of donkey.
 
>>Just go wank whatever language you think is better, asshole.
 
> Oh dear, is it your time of the month buttercup? :)
 
Why don't you go fuck yourself, asshole?
Juha Nieminen <nospam@thanks.invalid>: May 17 04:37PM

> ,--.,',' ,'----.__\ _( \----'
> '///,`,--.,' `-.__.--' `. )
> '///,' `-`
 
Why don't you just go fuck yourself, asshole?
Juha Nieminen <nospam@thanks.invalid>: May 17 04:38PM

>> A stupid response.
 
> No, I asked for practical reasons and not metaphors.
 
Why do you even bother talking to the asshole?
Keith Thompson <Keith.S.Thompson+u@gmail.com>: May 17 10:37AM -0700


> If you don't like the language, then don't use it. It's that simple.
> You can just go and fuck off. Go wank to whatever other language you think
> is so much better.
 
Juha, I've just added "MrSpook" to my killfile. I'm seriously
considering adding you as well. Please knock it off.
 
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips Healthcare
void Void(void) { Void(); } /* The recursive call of the void */
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