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245. Which operations onistream_iterator trigger input operations?
Section: 24.6.2 [istream.iterator] Status: NAD Submitter: Andrew Koenig Opened: 2000-05-02 Last modified: 2016-01-28
Priority: Not Prioritized
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Discussion:
I do not think the standard specifies what operation(s) on istream iterators trigger input operations. So, for example:
istream_iterator<int> i(cin);
int n = *i++;
I do not think it is specified how many integers have been read from cin. The number must be at least 1, of course, but can it be 2? More?
Rationale:
The standard is clear as written: the stream is read every time operator++ is called, and it is also read either when the iterator is constructed or when operator* is called for the first time. In the example above, exactly two integers are read from cin.
There may be a problem with the interaction between istream_iterator and some STL algorithms, such as find. There are no guarantees about how many times find may invoke operator++.
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