CODEWITHSUNDEEP
c++allocatoristream-iterator
Sreeraj Chundayil
Sreeraj Chundayil

Reputation: 5859

What's with allocator in vector?

vector<int> data(istream_iterator<int>(cin),
istream_iterator<int>{});   cout<<"Size is : " << data.size() << endl; //compile success

vector<int> data1(istream_iterator<int>(cin),
std::allocator<int>{});   cout<<"Size is : " << data1.size() << endl; //compile failure

 error: no matching function for call to ‘std::vector<int>::vector(std::istream_iterator<int>, std::allocator<int>)’    vector<int> data1(istream_iterator<int>(cin), std::allocator<int>{});

Why is the first statement fine but second? Doesn't the vector take int type allocator in this case? I am experimenting with allocators.

Upvotes: -1

Views: 308

Answers (1)

eerorika
eerorika

Reputation: 238431

Why is the first statement fine

Because vector has a constructor that accepts two iterators (and an allocator with default argument). Those iterators represent beginning and end of an input range.

but second [is not]?

Because vector doesn't have a constructor that accepts a single iterator and an allocator.

Upvotes: 5

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