CODEWITHSUNDEEP
c++iterator
Daniel Rosenthal
Daniel Rosenthal

Reputation: 1386

Can list's iterator return a non-const reference?

I'm super new to C++. I need to write a Linked List class that uses list. I'm most of the way there, but I need a [] operator that returns the nth element in the list. I have this working in most cases, but in my test driver I need to compare two elements from different lists. (I.e. l1[n]==l2[m]). This gives the following compile error:

error: passing ‘const StrList {aka const TList<std::basic_string<char> >}’ as ‘this’ argument of ‘T& TList<T>::operator[](int) [with T = std::basic_string<char>]’ discards qualifiers [-fpermissive]

I think the problem here is that my return call from the iterator in the [] operator is returning a const reference. (The return call from the [] operator is return(*iter);, where *iter refers to the correct element.

Is there a way to return the reference to the iterator as a non-const reference, or is there some other way I should be going about this? I can post more code if it's necessary.

Upvotes: 0

Views: 233

Answers (1)

Yuushi
Yuushi

Reputation: 26040

It's slightly hard to tell without code, but given the error, you likely need a const overload of operator[]:

template <typename T>
const T& operator[](std::size_t n) const
{
     ...
}

Upvotes: 4

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