Re: stl copy and istream_iterator and operator >>

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From	Ian Collins <ian-news@hotmail.com>
Newsgroups	comp.lang.c++
Subject	Re: stl copy and istream_iterator and operator >>
Date	Mon, 19 Sep 2011 10:00:47 +1200
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On 09/19/11 09:53 AM, persres@googlemail.com wrote:
> On Sep 18, 10:47 pm, Ian Collins<ian-n...@hotmail.com>  wrote:
>> On 09/19/11 09:27 AM, pers...@googlemail.com wrote:
>>
>>> Hi,
>>>       I have the following code -
>>
>>> string str("12 3213 asdf 21");
>>> vector<int>    v;
>>
>>> copy(istream_iterator<int>(istringstream(str)) ,
>>> istream_iterator<int>(),  back_inserter(v) );
>>
>> This shouldn't compile. You can't create an istream_iterator from a
>> temporary.
>>
>>> I expected copy to throw because the operator>>    would have failed due
>>> to the 'asdf' string present.
>>
>> Which operator>>?
>>
>>> However, it doesn't throw.  Do you know why,
>>
>> Because the code doesn't do what you think it does (assuming you get it
>> to compile).  Have a look at the vector contents.
>>
>>> How can i get it to throw or return an errror.
>>
>> You can provide your own input iterator type.

Please don't quote signatures

> It does compile and works as expected. This is standard way of
> copying.

I'd better try it then...

cat x.cc
#include <vector>
#include <iostream>
#include <string>
#include <sstream>
#include <iterator>

using namespace std;

int main() {
   string str("12 3213 asdf 21");
   vector<int> v;

   copy(istream_iterator<int>(istringstream(str)) ,
        istream_iterator<int>(),  back_inserter(v) );
}

g++ x.cc

x.cc: In function ‘int main()’:
x.cc:13:48: error: no matching function for call to 
‘std::istream_iterator<int>::istream_iterator(std::istringstream)’

CC x.cc
"x.cc", line 13: Error: Cannot cast from std::istringstream  to 
std::istream_iterator<int, char, std::char_traits<char>, int>.

-- 
Ian Collins

Thread

stl copy and  istream_iterator and operator >> "persres@googlemail.com" <persres@gmail.com> - 2011-09-18 14:27 -0700
  Re: stl copy and  istream_iterator and operator >> Ian Collins <ian-news@hotmail.com> - 2011-09-19 09:47 +1200
    Re: stl copy and istream_iterator and operator >> "persres@googlemail.com" <persres@gmail.com> - 2011-09-18 14:53 -0700
      Re: stl copy and istream_iterator and operator >> Ian Collins <ian-news@hotmail.com> - 2011-09-19 10:00 +1200
        Re: stl copy and istream_iterator and operator >> "persres@googlemail.com" <persres@gmail.com> - 2011-09-18 15:11 -0700
          Re: stl copy and istream_iterator and operator >> red floyd <no.spam.here@its.invalid> - 2011-09-18 15:23 -0700
          Re: stl copy and istream_iterator and operator >> Ian Collins <ian-news@hotmail.com> - 2011-09-19 10:23 +1200
            Re: stl copy and istream_iterator and operator >> James Kanze <james.kanze@gmail.com> - 2011-09-19 15:19 -0700
    Re: stl copy and  istream_iterator and operator >> Ian Collins <ian-news@hotmail.com> - 2011-09-19 10:11 +1200

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