assigning^constructing a c++obj: a few diff

Assignment operator is a field-by-field and bitwise overwrite [1] without eating up new memory. Both LHS and RHS must be (preexisting) objects with addresses.

A constructor always eats up (heap or stack) new memory, and reduces free memory.

[1] If a field is a pointer, then the same address is put into the LHS’s field bitwise. LHS and RHS both point to the same address — shallow copy.

Q: what if a field is a reference?
A: Can’t reassign. Default op= will trigger an error (compile time or runtime).
A: reference field is rare.

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