With the defined function as...
void func (int a [3]) { ... }
I'd like to be able to pass a dynamic static array like so
func (new int [3] {1,2,3});
instead of...
int temp [3] = {1,2,3};
func(temp);
Is this possible with C++?
3 Answers
If you have a C++11 compiler, func (new int [3] {1,2,3}); would work fine (but, remember that you are responsible for deleteing the memory). With gcc, just pass the -std=c++11 flag.
However, look into std::array so you don't have to use new:
Example
void func (std::array<int, 3> a)
{
}
int main()
{
func({{1, 2, 3}});
}
7 Comments
Ed Swangren
"would work fine" as in "the code runs and produces the expected output, but leaks memory because there is no matching call to
delete in the example"
Jesse Good
@EdS.: Right, I added a note about that.
xori
So does the compiler put that declaration on the heap?
Jesse Good
@EdS.: The elements of
std::array are on the stack if you instantiate std::array on the stack. See here. It's basically a struct with an array as a member.Ed Swangren
Oh wow, now that I did not know, thanks. I can't say I've ever actually used std::array, but I routinely learn new things browsing around questions here. Thanks again. +1
|
It works on my compiler (Eclipse indigo with CDT extension), but it gives a warning that implies it may not work in all environments:
extended initializer lists only available with -std=c++0x or -std=gnu++0x [enabled by default]
Here's my test code:
void func (int a[3])
{
cout << a[2];
}
int main()
{
func(new int[3]{1,3,8});
}
successfully prints "8" to the console.
Comments
Your example with new int [3] {1,2,3} works just fine, but it allocates an array on the heap each time it is called.
You should be able to do it on the stack using a typecast:
func((int[]){1,2,3});
3 Comments
Jesse Good
I believe
(int[]){1,2,3} is only in C (it's a compound literal).
scientiaesthete
@JesseGood GCC supports compound literals in C++, though the semantics are somewhat different than in C.
Prokop Hapala
it works with
const ... e.g. double arr_func( int n, const double * xs ){ }; arr_func( 3, (const double[]){1.0,2.0,3.0} );
newmeans heap (by default).