Can't I Store Arrays Directly in C Vectors? Why Use `std::array` Instead?

Working with Vectors and Arrays: Understanding Type Compatibility

When working with data structures, it's crucial to understand the compatibility and limitations of various types. In C , it's not uncommon to encounter situations where storing arrays within a vector raises questions about proper usage.

The Issue:

Consider a scenario where you attempt to define a vector holding arrays, as shown below:

vector<float[4]> myVector;

Upon resizing the vector, you may encounter an error stating, "conversion from 'int' to non-scalar type 'float [4]' requested." This error highlights the underlying issue.

The Solution:

Arrays, unlike other fundamental data types like integers or doubles, are not inherently copy-constructible or assignable. This means they cannot be placed into containers like vectors. To overcome this limitation and store arrays in vectors, you must use an array class template.

Alternative Option: Using an Array Class Template

Array class templates provide a solution to this problem. They offer array-like functionality while ensuring compatibility with containers. Here's an example using the std::array template:

std::vector<std::array<double, 4>> myVector;

This declaration correctly utilizes the std::array class template, allowing you to store arrays of four doubles within a vector. You can resize and manipulate this vector as needed, without encountering the same errors faced with basic arrays.

Additional Templates:

Apart from std::array, there are other array class templates to choose from:

• std::tr1::array: Part of the C Technical Report 1 (TR1), this template has similar functionality to std::array.
• boost::array: Provided by the Boost libraries, this template offers even more flexibility than the previous two options.

Ultimately, the choice of array class template depends on your specific requirements and the version of C you're using.

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