Re: index operator[] overloading

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Tue, 29 May 2007 15:47:22 -0400
Message-ID:
<f3i00b$obr$1@news.datemas.de>
Project X wrote:

On May 29, 7:30 pm, Zeppe
<zep_p@.remove.all.this.long.comment.yahoo.it> wrote:

Bart Simpson wrote:

Thanks Zeppe that clarifies that.

So to implement it one has to implement BOTH of these?

myTypeoperator[](constsize_t)const;
myType&operator[](constsize_t);


exactly, and the compiler will chose the proper one based on the
"const". Another hint: the method


To the much of my surprise, I tried this and the non-constant version
is always called. Here is the code:

#include <iostream>

class MyArray
{
public:
MyArray(const size_t size) : m_size(size) {
arr_ = new double[size];
}

~MyArray() {
if (arr_) delete[] arr_ ;
}

double& operator[](const size_t idx)
{
std::cout << "LHS" << std::endl;
return arr_[idx];
}

const double& operator[](const size_t idx) const
{
std::cout << "RHS" << std::endl;
return arr_[idx];
}

double *arr_;
size_t m_size;
};

int main(int argc, char** argv) {
MyArray a(3);
a[0] = 8.0;
std::cout << a[0] << std::endl;
return 0;
}

The output in both cases is "LHS". What's wrong?


Nothing. 'a' is declared non-const. Why would a const function
be called when non-const is available?

V
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