CODEWITHSUNDEEP
c++arrays
Larrimus
Larrimus

Reputation: 211

Problems with a Dynamic Array of Static Arrays

I do not plan on changing the size of my dynamic array. The reason I want to create a dynamic array of static arrays (which contain shorts) is so that I can return that array in a function (not defining the size of that array until I'm in that function).

My first question then, is how do I return such an array? Functions don't let you return a pointer without a type & I'm unable to find out how to define a pointer with type array.

This brings me to my second question, which is how do I correctly define a dynamic array of static arrays? I have searched for this online, but none of the answers have been too helpful.

One way to do it is to declare: short (*array)[size] but the problem with this is that I don't know how to initialize the array in that case, and size has to be a literal.

I could do this:

typedef short column[size];
column * row = NULL;
row = malloc(rowMax * sizeof(column));
row[0][0] = 10;

but again, size has to be a literal; and even if size is a literal, I receive an error stating that a value of type "void *" cannot be assigned to an entity of type "column *".

If any of you have a solution that doesn't use vectors that would be greatly appreciated; as the vector class is larger than the array class.

Upvotes: 1

Views: 324

Answers (2)

bleepbloop
bleepbloop

Reputation: 81

For the sake of saving time, just create a vector of static arrays

std::vector<std::array<Type, n>>

Not sure why the size difference matters, it's only a few Kb.

Also, if you're going to write C code in a C++ app... you're gunna have a bad time.

Upvotes: 1

jotik
jotik

Reputation: 17940

In C++11 one could use std::array from <array> and do:

constexpr std::size_t const cols = 42u; // static size
using MyStaticArray = std::array<short, cols>; // static array type
// Or in C++03 and earlier: typedef short MyStaticArray[42u];

std::size_t const rows = someValue; // dynamic size
MyStaticArray * dynamicArray = new MyStaticArray[rows];
// Or better: std::vector<MyStaticArray> dynamicArray(rows);

for (std::size_t row = 0u; row < rows; ++row)
  for (std::size_t col = 0u; col < cols; ++col)
    dynamicArray[row][col] = rows * cols;

PS: Also give upvotes to Remy Lebeau below for his comments helped to improve this post.

Upvotes: 2

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