How to Convert Vector to Array

How to convert vector to array

There's a fairly simple trick to do so, since the spec now guarantees vectors store their elements contiguously:

std::vector<double> v;
double* a = &v[0];

Converting a vector to an array - Is there a 'standard' way to do this?

Yes, that behavior is guaranteed. Although I can't quote it, the standard guarantees that vector elements are stored consecutively in memory to allow this.

There is one exception though:

It will not work for vector<bool> because of a template specialization.

http://en.wikipedia.org/wiki/Sequence_container_%28C%2B%2B%29#Specialization_for_bool

This specialization attempts to save memory by packing bools together in a bit-field. However, it breaks some semantics and as such, &theVector[0] on a vector<bool> will not work.

In any case, vector<bool> is widely considered to be a mistake so the alternative is to use std::deque<bool> instead.

C++ how to convert vector to an array?

You do not need (and should not) dereference - the function you call expects arrays, and you pass their first elements. Use

gsl_spline_init (spline, x_input_Array, y_input_Array, iNoOfPtsIni);

Fastest way to copy the contents of a vector into an array?

std::copy, hands down. It’s heavily optimised to use the best available method internally. It’s thus completely on par with memcpy. There is no reason ever to use memcpy, even when copying between C-style arrays or memory buffers.

AS3: How to convert a Vector to an Array

your approach is the fastest ... if you think it's to verbose, then build a utility function ... :)

edit:

To build a utility function, you will probably have to drop the type as follows:

function toArray(iterable:*):Array {
     var ret:Array = [];
     for each (var elem:Foo in iterable) ret.push(elem);
     return ret;
}

How to convert vector to array and access it

To begin with, you should understand how std::vector works: it is a self-expanding array, it can reallocate its internal storage whenever it needs.
A right way to get a pointer to internal array is to call std::vector::data member (available only in C++11):

double * a = v.data();

Note that this pointer is valid only until you modify the vector.
Just in case, "convert" here doesn't mean real conversion, the vector isn't modified and no new arrays are created. Only a pointer to the data stored in std::vector is received.

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