resize a pointer

[pozdrav]

hi, suppose i have a vector class like this.

template <class T>
class vec {
private:
	int length;
	T *v;
	
public:
	vec();		
        vec(int n);
        ....
        ....
        ~vec();
};

// zero argument constructor
template <class T>
vec<T>::vec() : length(0), v(0) {}

// 1-arg constructor
template <class T>
vec<T>::vec(int n) : length(n), v(new T[n]) {}

template <class T>
vec<T>::~vec() {
     if (v != 0) {
          delete[] (v);
     }
}

Here, under the 1-arg constructor I create a vector with length n using new. Now suppose I would like to resize this vector, say by removing the last 2 elements, say, then
1) Is it better to implement a resize/remove function as a member function here, for example, as,

vec<T> & remove(const int n, string index); // ex: n = 2, index = "last"  

or implement as a separate function template. I understand it can be done both ways, but I would like to know which one is better and why?

2) While implementing this function, say as a member function, how do I go about deleting just the last 2 elements of this vector? Is it possible without using a temporary array (for backup) and just do delete v[n-1]; delete v[n-2]; and reset the length property?

thank you!

[jsmith]

1. Such a function probably needs to access the internals of the object directly, so implementing
it as a member function would be preferred.

2. No, but you could do as std::vector<> does, and rename your length member to "num_used"
and create another member called "capacity", which keeps track of the number of elements
actually allocated.

[boolivar]

And sequential question - what about vector growing? ;-)

[kbw]

Have a look at the erase/remove idiom for std::vector.

[pozdrav]

jsmith, kbw,

thank you, I will look into it and implement similarly.