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Why does C++ support memberwise assignment of arrays within structs, but not generally?
Why is it that we can assign the object of one structure to other directly eg:
struct student s1,s2;
s2=s1 //is perfectly ok.
but we can not assign one array value to the other eg:
int a[10],b[10];
a=b //is not allowed.
though the element of structure may contain any no of arrays.
Please Explain.
This is how it is specified to be. If you need assignable arrays, use std::vector:
std::vector< int> a(10), b(10);
a = b;
The rule for default assignment operator for structs (and classes) is that it calls the assignment operators for base structs/classes and then the assignment operators for each data member.
Array assignment is not allowed at language level for purely historical reasons. Check also this question.
Ultimately, I don't think there is a reason that has much in the way of theoretical basis. I'd guess that it comes down to an expectation that arrays are typically large enough that preventing accidental copying was worthwhile.
By contrast, I think the expectation was that structs would typically be small enough that the convenience of supporting assignment outweighed the risk of possibly doing something unexpectedly expensive.