A question on C w.r.t arrays

Question

How does the code below not cause a compilation error?

int a[50]={0,1,4,[47]=47,48,49,50};

Answer 1

Bennett Post Amazing. I have never seen nor read about this before.

Is declaration order the only difference between C and C++ in this topic? Copied verbatim from the eel.is link: "designators for array elements and nested designators are not supported". Does this imply that the code posted by Ajeya is only valid in C and not C++?

I've just tested a few cases with C++.

int a[2] = {[1]=1}; // does not compile
int a[2] = {0, [1]=1}; // works fine
int a[2] = {[0]=1}; // works fine

Does this mean that all elements prior to the designator has to be initialized? Doesn't this defeat the purpose of using them?