file i/o with stream_iterators - error

[Aman]

Hi,
could you please tell me why the following program gives a compilation
error ? what does this error mean ?
note also that when i derefernce the iterator , the contents are
displayed.

int main()
{
ifstream ifs("file") ;
istream_iterato r<string> i_it(ifs) ;
copy(i_it.begin (), i_it.end(),ostr eam_iterator<st ring>(cout,"\n" )) ;
}
_______________ ____________
Complier error -
(SunOS 5.8 , g++ )
13 : no matching function for call to `istream_iterat or<basic_stri
ng<char,string_ char_traits<cha r>,__default_al loc_template<fa lse,0>[color=blue]
>,int>::begin ()'[/color]
13: no matching function for call to `istream_iterat or<basic_stri
ng<char,string_ char_traits<cha r>,__default_al loc_template<fa lse,0>[color=blue]
>,int>::end ()'[/color]
_______________ _______
regards,


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[Rob Williscroft]

Re: file i/o with stream_iterator s - error

Aman wrote in news:450f74dbb8 5ab55d80d1df17a a0dd289.26421
@mygate.mailgat e.org:
[color=blue]
> Hi,
> could you please tell me why the following program gives a compilation
> error ? what does this error mean ?
> note also that when i derefernce the iterator , the contents are
> displayed.
>
> int main()
> {
> ifstream ifs("file") ;
> istream_iterato r<string> i_it(ifs) ;
> copy(i_it.begin (), i_it.end(),ostr eam_iterator<st ring>(cout,"\n" )) ;[/color]


copy(
i_it,
istream_iterato r<string>(),
ostream_iterato r<string>(cout, "\n")
);

[color=blue]
> }
> _______________ ____________
> Complier error -
> (SunOS 5.8 , g++ )
> 13 : no matching function for call to `istream_iterat or<basic_stri
> ng<char,string_ char_traits<cha r>,__default_al loc_template<fa lse,0>[color=green]
>>,int>::begi n ()'[/color][/color]

Your trying to use an input iterator like its a container.

As I've done above use a default constructed istream_iterato r<string>
as the end iterator.

[color=blue]
> 13: no matching function for call to `istream_iterat or<basic_stri
> ng<char,string_ char_traits<cha r>,__default_al loc_template<fa lse,0>[color=green]
>>,int>::end ()'[/color]
> _______________ _______[/color]


HTH

Rob.
--

http://www.victim-prime.dsl.pipex.com/

[Aman Angrish]

Re: file i/o with stream_iterator s - error

[color=blue]
>
> copy(
> i_it,
> istream_iterato r<string>(),
> ostream_iterato r<string>(cout, "\n")
> );
>[/color]

That's neat .
[color=blue]
>
> HTH
>
> Rob.[/color]

Thanks Rob !,

regards,
Aman.




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[David Rubin]

Re: file i/o with stream_iterator s - error

Rob Williscroft wrote:

[snip][color=blue]
> copy(
> i_it,
> istream_iterato r<string>(),
> ostream_iterato r<string>(cout, "\n")
> );[/color]

Can you please explain why this works. I was under the impression that
the 'end' iterator had to be related to the 'begin' iterator in some
way. Thanks,

/david

--
Andre, a simple peasant, had only one thing on his mind as he crept
along the East wall: 'Andre, creep... Andre, creep... Andre, creep.'
-- unknown

[Adam Fineman]

Re: file i/o with stream_iterator s - error

David Rubin wrote:[color=blue]
> Rob Williscroft wrote:
>
> [snip]
>[color=green]
>> copy(
>> i_it,
>> istream_iterato r<string>(),
>> ostream_iterato r<string>(cout, "\n")
>> );[/color]
>
>
> Can you please explain why this works. I was under the impression that
> the 'end' iterator had to be related to the 'begin' iterator in some
> way. Thanks,
>[/color]

You snipped the declaration and definition of i_it, so here it is again:
------------------------------------------
ifstream ifs("file") ;
istream_iterato r<string> i_it(ifs) ;
------------------------------------------

The 'end' iterator of any istream_iterato r<T> is istream_iterato r<T>().
I'll agree that the syntax is not intuitive, as it looks like a call
to the default constructor, but that's something we all have to live with.

As another example, here is a program that fills a container from the
standard input:

-------------------------------------
#include <vector>
#include <string>
#include <iterator>
#include <iostream>

using namespace std;

int
main()
{
vector<string> v;

copy(istream_it erator<string>( cin),
istream_iterato r<string>(), // 'end' iterator
back_inserter(v ));

cout << "Recieved " << v.size() << " strings as input.\n";

return 0;
}
-------------------------------------

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[Julián Albo]

Re: file i/o with stream_iterator s - error

David Rubin escribió:
[color=blue][color=green]
> > copy(
> > i_it,
> > istream_iterato r<string>(),
> > ostream_iterato r<string>(cout, "\n")
> > );[/color]
>
> Can you please explain why this works. I was under the impression that
> the 'end' iterator had to be related to the 'begin' iterator in some
> way. Thanks,[/color]

Because the operator = that compares two istream_iterato r is written
that way, it gives a value of true when comparing one that has reached
his end to one default constructed. It's a simple solution that does not
need to define additional functions.

Regards.