CODEWITHSUNDEEP
c++sortingvectoriterator
CS Student
CS Student

Reputation: 1633

How does std::sort modify the backing type?

When I call sort on a vector of doubles using the begin() and end() iterators how does the sort function modify the original vector to contain the sorted values?

I though iterators simply represented a value, so how could they cause the original vector to get modified?

vector<double> nums = {10.33, 20.44, 60.77};
sort(nums.begin(), nums.end(); // how does the original nums get changed?

Upvotes: 4

Views: 124

Answers (1)

TartanLlama
TartanLlama

Reputation: 65630

An iterator doesn't represent the value, it represents some position in a container, stream, or stream buffer. Essentially, they are a generalization of pointers. Some iterators will let you modify what they are iterating over using indirection (*it).

In the simplest case, it could simply be a pointer. Consider this code:

vector<double> nums = {10.33, 20.44, 60.77};
double* it = &nums[0]; //get the address of the first element
++it; //increment the pointer
*it = 42; //assign 42 to nums[1]

An iterator provides much the same functionality (depending on the type of iterator).

vector<double> nums = {10.33, 20.44, 60.77};
vector<double>::iterator it = nums.begin();//get an iterator to the first element
++it; //increment the iterator
*it = 42; //assign 42 to nums[1]

Upvotes: 4

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