Interview questions

[cj]

Dear friends, I have one more questions for everyone in the newsgroup:

I am preparing for an interview on UNIX/C++. Could you please identify some
of the most important questions which might be asked, so that I could best
prepare for it?

Thank you,
C++J

[CFG]

I still don't understand why you've picked this question?
Just for the sake of the fancy term "POD", which you already know?

This question is definitely not the best single question about C++.

[Ioannis Vranos]

CFG wrote:

I still don't understand why you've picked this question?
Just for the sake of the fancy term "POD", which you already know?

This question is definitely not the best single question about C++.

As I said it would be one question of the many to determine the depth of
the candidate's knowledge. There would be simpler ones too. Since he
asked for a question that he could be asked, I chose to provide a
difficult one and not an easy one, that it would be certain he would
answer. And he learned new things, so why is it bad?


Regards,

Ioannis Vranos

[Ioannis Vranos]

cj wrote:

Dear friends, I have one more questions for everyone in the newsgroup:

I am preparing for an interview on UNIX/C++. Could you please identify some
of the most important questions which might be asked, so that I could best
prepare for it?

Another interesting question that I would ask, in the advanced level
this one.


In a class hierarchy with virtual member functions, how much does the
time cost of calling a virtual function increases while the depth of
abstraction increases?
For example:
class base1
{
// ...
virtual void something();
};

class base2: public base1
{
// ...
void something();
};

//...

class base999999: public base999998
{
// ...
void something();
};
base1 *p1=new base78;

p1->something();
base1 *p2=new base999999;

p2->something();

How much more time it takes for the implementation to find and invoke
base999999::som ething() in comparison to base78::somethi ng()?


Regards,

Ioannis Vranos

[Peter Koch Larsen]

"Ioannis Vranos" <iv*@guesswh.at .grad.com> skrev i en meddelelse
news:cb******** ***@ulysses.noc .ntua.gr...

cj wrote:

Dear friends, I have one more questions for everyone in the newsgroup:

I am preparing for an interview on UNIX/C++. Could you please identify some of the most important questions which might be asked, so that I could best prepare for it?

Thank you,
C++J

Here is one I would ask:
Is the following code guaranteed to be safe and portable?

#include <string>
#include <vector>
#include <cstddef>

int main()
{
using namespace std;

class A
{
vector<int>arra y;
string s;

public:
A():array(100){ }
}a;
unsigned char *p=reinterpret_ cast<unsigned char *>(&a);

unsigned char *v=new unsigned char[sizeof(a)];
for(size_t i=0; i<sizeof(a); ++i)
v[i]=p[i];
}

I do believe that that question is a very bad one. The code above is
obviously portable, but these casts do confuse. What on earth are you going
to do with v? Any programmers instinct is that code must have "a use", and
it is quite difficult to see what you could portable do with v. Also, the
reinterpret_cas t is to a non-const pointer which chould also give all of us
an uneasy feeling. Don't do that against those poor could-be collegues!

Kind regards
Peter

[Peter Koch Larsen]

"Ioannis Vranos" <iv*@guesswh.at .grad.com> skrev i en meddelelse
news:cb******** ***@ulysses.noc .ntua.gr...

cj wrote:

Dear friends, I have one more questions for everyone in the newsgroup:

I am preparing for an interview on UNIX/C++. Could you please identify some of the most important questions which might be asked, so that I could best prepare for it?
Another interesting question that I would ask, in the advanced level
this one.


In a class hierarchy with virtual member functions, how much does the
time cost of calling a virtual function increases while the depth of
abstraction increases?

[snip]

How much more time it takes for the implementation to find and invoke
base999999::som ething() in comparison to base78::somethi ng()?

Regards,

Ioannis Vranos

That one was much better! ;-)

/Peter

[E. Robert Tisdale]

Ioannis Vranos wrote:

Another interesting question that I would ask
in the advanced level is this one.

In a class hierarchy with virtual member functions,
how much does the time cost of calling a virtual function increases
while the depth of abstraction increases?

For example:

class base1 {
// ... public: virtual void something(void) ;
};

class base2: public base1 {
// ... public: void something();
};

//...

class base999999: public base999998 {
// ... public: void something();
};

base1 *p1=new base78;

p1->something();

base1 *p2=new base999999;

p2->something();

How much more time it takes
for the implementation to find and invoke base999999::som ething()
in comparison to base78::somethi ng()?

It depends upon the implementation (compiler).
In the typical implementation, it takes no more time.
The C++ computer programming language standard
does *not* specify implementations , performance or efficiency.

[Ioannis Vranos]

E. Robert Tisdale wrote:

How much more time it takes for the implementation to find and invoke
base999999::som ething()
in comparison to base78::somethi ng()?

It depends upon the implementation (compiler).
In the typical implementation, it takes no more time.
The C++ computer programming language standard
does *not* specify implementations , performance or efficiency.

Wrong. Next please. :-)


Regards,

Ioannis Vranos

[Ioannis Vranos]

Ioannis Vranos wrote:

E. Robert Tisdale wrote:

How much more time it takes for the implementation to find and invoke
base999999::som ething()
in comparison to base78::somethi ng()?

It depends upon the implementation (compiler).
In the typical implementation, it takes no more time.
The C++ computer programming language standard
does *not* specify implementations , performance or efficiency.

Wrong. Next please. :-)

But I forgot to give you a reference. "The C++ Programming Language" 3rd
Edition or Special Edition, page 324.


Regards,

Ioannis Vranos

[JKop]

Peter Koch Larsen posted:

I do believe that that question is a very bad one. The code above is
obviously portable, but these casts do confuse. What on earth are you
going to do with v? Any programmers instinct is that code must have "a
use", and it is quite difficult to see what you could portable do with
v.

What ever happened to just having fun?

int main(void)
{
int monkeys[7] = { 3, 4 ,3, 2 ,2 ,34, 23 ,3 };

char jack reinterpret_cas t<char>(monkey s[5]);

cout << jack;
}

[JKop]

JKop posted:

Peter Koch Larsen posted:

I do believe that that question is a very bad one. The code above is
obviously portable, but these casts do confuse. What on earth are you
going to do with v? Any programmers instinct is that code must have "a
use", and it is quite difficult to see what you could portable do with
v.
What ever happened to just having fun?

int main(void)
{
int monkeys[7] = { 3, 4 ,3, 2 ,2 ,34, 23 ,3 };

char jack reinterpret_cas t<char>(monkey s[5]);

TYPO

char jack = reinterpret_cas <char>(monkey s[5]);


cout << jack;
}