C++ template function returning "vector" ?

Lost User

I am trying to get comfortable using "vector". I have a function "returning" hardware parameters I need to process further "upstream" - including "main". I can pass a vector by reference or have been told to define "local vector" and "return" if from the function. I am not sure how "return vector" really works and have not tried it yet. The function returning "vector " syntax is scary... Could I return pointer to locally defined vector ? ( Or is is even feasible ?) Is there a specific resource I could read ? Something similar to this example , but with "return * vector - string "?

// C++ program to demonstrate how vectors
// can be passed by reference.
#include
using namespace std;

// The vect is passed by reference and changes
// made here reflect in main()
void func(vector &vect)
{
vect.push_back(30);
}

int main()
{
vector vect;
vect.push_back(10);
vect.push_back(20);

func(vect); 

for (int i=0; i

Greg Utas

Your code looks good to me. If you want func to return a vector, it should allocate it on the heap, and returning it in a unique_ptr would be better than just returning a raw pointer. But it looks like you want to update a vector that might already have entries, so passing it by reference makes sense. EDIT: func isn't a function template; it simply takes a vector argument. The term function template refers to a function defined by template func...

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CPallini

You function is OK as it stands.

Quote:

can pass a vector by reference or have been told to define "local vector" and "return" if from the function.

That is fine whenever you have code similar to

vector get_rand_vect(size_t size)
{
vector v;
while (size--)
{
v.push_back(rand());
}
return v; // this is optimized by the compiler
}

"In testa che avete, Signor di Ceprano?" -- Rigoletto

Lost User

That would not work in my function which retrieves unknown "size" of (string) data. As I said, I want to learn about vector , but more I look into it the more I like "old fashioned way " to pass a pointer to the function and let the calling code process the pointer afterwards. Seems much simpler.

Lost User

Vectors are quite simple, but very powerful. But the usage will depend on what you are actually trying to do. In your example your func method does nothing useful, so it is not clear what actual problem you are trying to solve.

CPallini

Quote:

That would not work in my function which retrieves unknown "size" of (string) data.

That's not a problem. It would work as well. Try, for instance

#include #include using namespace std;

vector get_a_fresh_vector_with_unknown_size()
{
vector v;
int N = rand() % 128;

for (int n = 0; n < N; ++n)
v.push_back( rand() );

return v;
}

int main()
{
auto v = get_a_fresh_vector_with_unknown_size();
for (auto x : v)
cout << x << " ";
cout << endl;
}

"In testa che avete, Signor di Ceprano?" -- Rigoletto