Menu
Hello I am comming from c to c++ and I've been wondering why can std::vector be passed by value.
I assume passing dynamicaly allocated array by value is not possible as that would only copy the pointer.
How is it then possible for a vector to be coppied, if inside of a vector class is same pointer. It has to somehow know how to reconstruct it into another object.
579
The conclusion is that arrays of integers are faster than vectors of integers (5 times in my example). However, arrays and vectors are arround the same speed for more complex / not aligned data.
It is highly unlikely that you'll see an appreciable performance difference between a dynamic array and a vector since the latter is essentially a very thin wrapper around the former. Also bear in mind that using a vector would be significantly less error-prone.
A std::vector can never be faster than an array, as it has (a pointer to the first element of) an array as one of its data members. But the difference in run-time speed is slim and absent in any non-trivial program. One reason for this myth to persist, are examples that compare raw arrays with mis-used std::vectors.
Vector are implemented as dynamic arrays with list interface whereas arrays can be implemented as statically or dynamically with primitive data type interface. Size of arrays are fixed whereas the vectors are resizable i.e they can grow and shrink as vectors are allocated on heap memory.
std::vector knows how many elements are stored in the dynamic memory. It is a simple matter to allocate a new buffer of that size and copy the contents into that new memory. All of this happens in the copy constructor.
182
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
