Question

I have something like this:

typedef int customType[10];

And I want a function like this

std::vector<customType*>& myFunc();

But there are some problems.

1) I need to allocate memory for every pointer to customType in the vector (do I?)
and doing

std::vector<customType*> A;
//some code to get length
for (i = 0; i < length; i++)
{
  A[i]  = new customType;
}

is wrong because of an error:

IntelliSense: a value of type "int *" cannot be assigned to an entity of type "customType*"

2) In common, is it a good way to store such data? Maybe I should make an array of 1 dimension with everything stored in one line and use something like

A[i*innerLength+j]

to access elements?

Answer 1

I would generally recommend using something like the below and doing the array indexing yourself.

std::vector<int> vals(row_size*col_size, 0);

At really large sizes it may be better to break it up. It’s just a lot of contiguous memory to allocate in a block. “Really large” is pretty subjective, and you probably can get away with a lot larger sizes than most people would expect. Let the profiler tell you when it’s a problem.

If you have access to C++11, then this would be another option.

TEST(array)
{
    typedef std::array<int,10> Foo;
    typedef std::vector<Foo> Foos;
    Foos foos(10, Foo());
}