性能：重载[]和对函数的调用

Question

My initial thought over the performance of calling an over loaded [] to acquire a member data and calling a function like getData(index) would be the same. Since calling [] is essentially a function call. Assume they acquire the same data like values[1] and values.getData(1) would return the same value. Am I wrong? If they perform the same, is there a non-performance advantage to using [] in this case?

Answer 1

They are the same, under the hood. Overloaded operators are just a unique syntax for a function call. The only thing changing is the appearance of code that calls it.

You're even allowed to force the operator calls to look function-like.

values[1]

may also be written as

values.operator[]( 1 )
//     ^^^^^^^^^^ This is effectively the name of your function.

Answer 2

Both are the same thing, as you also mention in your question. Overloads are just function calls. No performance gain.

However, operator[] historically means that (or is expected to have) there is a contiguous formation of internal data representation in the memory, or more generally serve as an index to container like data structures. Thus, it is generally implemented in classes like vectors, arrays, matrices, etc.