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Re:C99 doesn't need function bodies, or 'VLAs are Turing com... by tstanisl on Friday August 05, 2022 @06:19AM (#32354049)
There are multiple false myths about VLAs. Please known that VLA is about the typing not about the storage.

The line:

    typedef int T[n];
is the essence of VLA-ness, not `int A[n]`. The array of VLA type can have any kind of storage one wants.

It can be stack

    T a;
It can be heap

    T *a = malloc(sizeof *a);
It can be even infamous alloca()

    T *a = alloca(sizeof *a);
Please stop talking about this "VLA is stack-base vector" crap because it means that one does not understand what VLAs are about. I admin that automatic VLAs are pretty much always wrong but this use case is a tiny bit of the realy functionality of VLA types.

VLA were added to language to handle multidimensional arrays.

And the really shine at this task. Even C++ has not good alternative for it. Vector of vectors is a really crappy data structure.

A few examples when working with square matrices:

- allocation on stack

    float A[n][n];
- allocation on heap

    float (*A)[n] = malloc(sizeof(int[n][n]));
    ...
    free(A);
- indexing

    A[i][j]
- passing to functions:

    void add(int n, float A[static n][n], float B[static n][n], float RES[restrict static n][n]);

    ...
Please show me something as simple, effective, self-documenting and elegant in C++.

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