CODEWITHSUNDEEP
c++dictionaryiterator
K. Shores
K. Shores

Reputation: 1005

Getting an iterator to a const map<char, int>

So, I am trying to get an iterator to a map that I am passing in as a const reference to a function. My compiler complains when I do something like this:

bool func(string s, const map<char, int>& m){
    std::map<char, int>::iterator it = m.begin();
    /*more code here...*/
}

How should I do this?

The error message is:

error: no viable conversion from 'const_iterator' (aka '__map_const_iterator<typename __base::const_iterator>') to 'std::map<char, int>::iterator'
  (aka '__map_iterator<typename __base::iterator>')
    std::map<char, int>::iterator it = m.begin();

Upvotes: 2

Views: 2553

Answers (2)

NathanOliver
NathanOliver

Reputation: 180500

The issue here is m is const so m.begin() returns a const_iterator not an iterator. You either need to use:

std::map<char, int>::const_iterator it = m.begin();

Or for simplicity use auto and you have:

auto it = m.begin();

Upvotes: 5

Slava
Slava

Reputation: 44238

You should use const_iterator instead:

std::map<char, int>::const_iterator it = m.begin();

Upvotes: 2

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