to improve programming in pointers

[sivashankar21]

how i can improve my programming skill in pointer using c++

 

[benben]

by more reading and practices.

Ben

 

[Gianni Mariani]

how i can improve my programming skill in pointer using c++

Go find the answers to these questions.


struct A { int a; };

struct B : A { int b; };

A xa[ 10 ];
B xb[ 10 ];

A * pa = xb;
// Q1 - what is the value of pa pointing to ?

A * pBAD = pa + 1;
// Q2 - why is pBAD, bad ?

B * pb = xb;
// - same as Q1

A * paOK = pb + 1;
// Q3 - what does paOK point to ?


A (&( * pf )( int * ))[ 10 ];
// Q4 - what is pf ?

A * paX = & pb[1];

bool b( paX == paOK );
// Q5 - what is the value of b

A * paY = & pb[3];

int iNOTGOOD( paY - paX );
// Q6 - Why is iNOTGOOD not good ?

A * paM = new B;

int main()
{

delete paM; // line Z - NOT GOOD
// Q7 - why is line Z a bad thing ?

paM = 0;
// Q8 - what is paM now ?

delete paM;
// Q9 - what does delete paM do ?

bool x( & (* xb).b == & xb->b );
// Q10 - What is the value of x ?
}

B * F()
{
B x[2];

return x; // doh !
// Q11 - Why is the line marked "doh" broken ?
}

 

[loufoque]

(e-mail address removed) a écrit :

how i can improve my programming skill in pointer using c++

You shouldn't even use pointers.
Avoid them as much as possible and only use them when it's needed.

 

[Default User]

(e-mail address removed) a écrit :

You shouldn't even use pointers.
Avoid them as much as possible and only use them when it's needed.

At which point he won't know how to use them.



Brian

 

[Ian Collins]

loufoque wrote:




At which point he won't know how to use them.

But he may have developed sufficient skill in in avoiding them so he
doesn't have to!

Are there any (real world) instances where pointers can't be avoided?

 

[Gianni Mariani]

Ian Collins wrote:
....

Are there any (real world) instances where pointers can't be avoided?

Let's see:

a) the "this" keyword.

b) When you may or may not want to pass an interface ... e.g.

void DoThing( const A & a, ErrorReporter * e = 0 );

c) Intrusive reference counted objects.

d) When objects point to one another i.e. a<->b

+ many more

 

[Ian Collins]

Ian Collins wrote:
....



Let's see:

a) the "this" keyword.

b) When you may or may not want to pass an interface ... e.g.

void DoThing( const A & a, ErrorReporter * e = 0 );

c) Intrusive reference counted objects.

d) When objects point to one another i.e. a<->b

+ many more

With the exception of a, all these can be replace by some form of smart
pointer object.

 

[Gianni Mariani]

Ian Collins wrote:
....

With the exception of a, all these can be replace by some form of smart
pointer object.

You still need to understand pointers even if you're managing them using
smart pointers.

 

[Ian Collins]

Ian Collins wrote:
....



You still need to understand pointers even if you're managing them using
smart pointers.

True enough, but I was trying to think of an example where raw pointers
can't be replaced with smart pointers.

 

[benben]

True enough, but I was trying to think of an example where raw pointers

can't be replaced with smart pointers.

When you are writing your own smart pointers? Perhaps?

Ben