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Help with reading formatted input from an istream

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  Help with reading formatted input from an istream Ttodir <sanmrtn96@gmail.com> - 2012-01-26 18:12 -0800
    Re: Help with reading formatted input from an istream Ian Collins <ian-news@hotmail.com> - 2012-01-27 20:21 +1300
    Re: Help with reading formatted input from an istream Leigh Johnston <leigh@i42.co.uk> - 2012-01-27 12:47 +0000
      Re: Help with reading formatted input from an istream Ttodir <sanmrtn96@gmail.com> - 2012-01-28 11:02 -0800

#13601 — Help with reading formatted input from an istream

Consider the following program:

#include <iostream>
#include <iterator>
#include <string>
#include <set>
#include <algorithm>

using namespace std;

typedef string T; // to simplify, always consider T as string

template<typename input_iterator>
void do_something(const input_iterator& first, const input_iterator&
last) {
    const ostream_iterator<T> os(cout, "\n");
    const set<T> words(first, last);
    copy(words.begin(), words.end(), os);
}

int main(int argc, char** argv) {
    const istream_iterator<T> is(cin), eof;
    do_something(is, eof);
    return 0;
}

The program extracts all the words from an istream (cin) and does
something with them. Each word is seperated by a white space by
default. The logic behind the formatted extraction is inside the
istream_iterator.

What I need to do now is to pass to do_something() two iterators so
that the extracted words will be separated by a punctuation character
instead of a white space (white spaces will be considered as "normal"
characters). How would you do that in a "clean C++ way" (that is, with
the minimum effort)?

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#13605

On 01/27/12 03:12 PM, Ttodir wrote:
> Consider the following program:
>
> #include<iostream>
> #include<iterator>
> #include<string>
> #include<set>
> #include<algorithm>
>
> using namespace std;
>
> typedef string T; // to simplify, always consider T as string
>
> template<typename input_iterator>
> void do_something(const input_iterator&  first, const input_iterator&
> last) {
>      const ostream_iterator<T>  os(cout, "\n");
>      const set<T>  words(first, last);
>      copy(words.begin(), words.end(), os);
> }
>
> int main(int argc, char** argv) {
>      const istream_iterator<T>  is(cin), eof;
>      do_something(is, eof);
>      return 0;
> }
>
> The program extracts all the words from an istream (cin) and does
> something with them. Each word is seperated by a white space by
> default. The logic behind the formatted extraction is inside the
> istream_iterator.
>
> What I need to do now is to pass to do_something() two iterators so
> that the extracted words will be separated by a punctuation character
> instead of a white space (white spaces will be considered as "normal"
> characters). How would you do that in a "clean C++ way" (that is, with
> the minimum effort)?

Derive your own input iterator class from std::input_iterator.

-- 
Ian Collins

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#13607

On 27/01/2012 02:12, Ttodir wrote:
> Consider the following program:
>
> #include<iostream>
> #include<iterator>
> #include<string>
> #include<set>
> #include<algorithm>
>
> using namespace std;
>
> typedef string T; // to simplify, always consider T as string
>
> template<typename input_iterator>
> void do_something(const input_iterator&  first, const input_iterator&
> last) {
>      const ostream_iterator<T>  os(cout, "\n");
>      const set<T>  words(first, last);
>      copy(words.begin(), words.end(), os);
> }
>
> int main(int argc, char** argv) {
>      const istream_iterator<T>  is(cin), eof;
>      do_something(is, eof);
>      return 0;
> }
>
> The program extracts all the words from an istream (cin) and does
> something with them. Each word is seperated by a white space by
> default. The logic behind the formatted extraction is inside the
> istream_iterator.
>
> What I need to do now is to pass to do_something() two iterators so
> that the extracted words will be separated by a punctuation character
> instead of a white space (white spaces will be considered as "normal"
> characters). How would you do that in a "clean C++ way" (that is, with
> the minimum effort)?

The "clean C++ way" would be to imbue your own ctype facet which lets 
you classify what exactly is white space.

/Leigh

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#13629

On Jan 27, 12:47 pm, Leigh Johnston <le...@i42.co.uk> wrote:
> On 27/01/2012 02:12, Ttodir wrote:
>
>
>
>
>
>
>
>
>
> > Consider the following program:
>
> > #include<iostream>
> > #include<iterator>
> > #include<string>
> > #include<set>
> > #include<algorithm>
>
> > using namespace std;
>
> > typedef string T; // to simplify, always consider T as string
>
> > template<typename input_iterator>
> > void do_something(const input_iterator&  first, const input_iterator&
> > last) {
> >      const ostream_iterator<T>  os(cout, "\n");
> >      const set<T>  words(first, last);
> >      copy(words.begin(), words.end(), os);
> > }
>
> > int main(int argc, char** argv) {
> >      const istream_iterator<T>  is(cin), eof;
> >      do_something(is, eof);
> >      return 0;
> > }
>
> > The program extracts all the words from an istream (cin) and does
> > something with them. Each word is seperated by a white space by
> > default. The logic behind the formatted extraction is inside the
> > istream_iterator.
>
> > What I need to do now is to pass to do_something() two iterators so
> > that the extracted words will be separated by a punctuation character
> > instead of a white space (white spaces will be considered as "normal"
> > characters). How would you do that in a "clean C++ way" (that is, with
> > the minimum effort)?
>
> The "clean C++ way" would be to imbue your own ctype facet which lets
> you classify what exactly is white space.
>
> /Leigh

thank you Leigh. That's really the thing to do.

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