C++ help

[Tauren]

cout << "\nYou trade your sword for a battle axe.";
    inventory[0] = "battle axe";
    cout << "\nYour items:\n";
    for (int i = 0; i < numItems; ++i)
        cout << inventory[i] << endl;

Uhh well the question is that I really dont get the ++i Why would you use the pre fix instead of the post fix, I know how they work its just doesnt really make sense

[mariocatch]

first, please post with code tags...

second, it's really use choice... it just increments the variable 'i' before it's accessed. may as well stick to "i++" imo.

[Infarction]

Some people have argued that ++i yields more efficient assembly code. When I checked, they were the same. In this situation, it doesn't matter.

[Tauren]

Ur right, If you had a server and maybe the data base which holds the items you wouldnt want the server holding the item before you got it I guess I will always just use i++

[Tauren]

I just dont fer what the statments do? whats the diffrence?

/code for (int i = 0; i < numItems; ++i)
what does that do like? lol explain

[Tauren]

i++ Would be increased before code is done
++i is increased before code is done

[vijayan121]

Some people have argued that ++i yields more efficient assembly code. When I checked, they were the same. In this situation, it doesn't matter.

in this specific case it really does not matter. When applied to primitives such
as int or char, they are indistinguishable in terms of efficiency. When applied
to objects of a user defined type the difference can be significant; the prefix
version avoids the creation of an anonymous temporary.

try this code:

int main()
{
  struct A
  {
    A( int ii ) : i(ii) { cout << "A::constructor\n" ; }
    A(const A& that ) : i(that.i) { cout << "A::copy_constructor\n" ; }
    ~A() { cout << "A::destructor\n" ; }
    A& operator++() // prefix
    { ++i ; return *this ; }
    A operator++(int) // postfix
    { A temp(*this); ++i ; return temp ; }
    operator int() const { return i ; }
    int i ;
  };
  cout << "-------------  start -----------------------------\n" ;
  A a1 = 100, a2 = 100 ;
  cout << "a1: " << a1 << "\ta2: " << a2 << '\n' ;
  cout << "-------------  prefix++  ------------------------\n" ;
  int i = ++a1 ; 
  cout << "a1: " << a1 << "\ti: " << i << '\n' ;
  cout << "-------------  postfix++  -----------------------\n" ;
  i = a2++ ;
  cout << "a2: " << a2 << "\ti: " << i << '\n' ;
  cout << "-------------  done -----------------------------\n" ;
};

and here is the output:
------------- start -----------------------------
A::constructor
A::constructor
a1: 100 a2: 100
------------- prefix++ ------------------------
a1: 101 i: 101
------------- postfix++ -----------------------
A::copy_constructor
A::destructor
a2: 101 i: 100
------------- done -----------------------------
A::destructor
A::destructor

we can really see the difference now between ++a1 and a2++, both
in terms of the difference in semantics as well as performance.

if you are into a lot of C++ programming, it is a good idea to get
into the habit of using the prefix versions of ++ and -- as the normal
case. even for builtin types like int, the prefix version is as efficient
as the postfix version.

[WaltP]

Ur right, If you had a server and maybe the data base which holds the items you wouldnt want the server holding the item before you got it I guess I will always just use i++

I just dont fer what the statments do? whats the diffrence?

/code for (int i = 0; i < numItems; ++i)
what does that do like? lol explain

Huh? Try using the PREVIEW button and proofreading your posts please. And please read this, too.

Try this program for illustration:

int main()
{
    int i = 5;

    cout << "        i = " << i << endl;
    cout << "prefix  i = " << ++i << endl;
    cout << "now     i = " << i << endl;
    cout << "postfix i = " << i++ << endl;
    cout << "now     i = " << i << endl;
    return 0;
}