C++ Range based stream

Question

Hoping somebody has knowledge of the range based additions going into the standard. So they can point out all the things I need to add to make it compliant.

IterableStream.h

#include <iostream>
#include <iterator>
namespace ThorsAnvil::Util
{
 
template<typename T>
class IterableStream
{
 std::istream& stream;
 public:
 IterableStream(std::istream& stream)
 : stream(stream)
 {}
 operator std::istream&() {return stream;}
 std::istream_iterator<T> begin() {return std::istream_iterator<T>(stream);}
 std::istream_iterator<T> end() {return std::istream_iterator<T>();}
};
}

Example usage

#include "IterableStream.h"
#include <iostream>
#include <fstream>
namespace TaU = ThorsAnvil::Util;
int main()
{
 std::ifstream x("plop");
 for(auto const& y: TaU::IterableStream<int>(x)) {
 std::cout << y << "\n";
 }
}

Answer 1

I don't like the name - it ought to be more explicit that it's an input-only range.

Otherwise, it looks just as a range should, with the observation that we omit the usual const iterators, as they don't make sense here.

I think you can avoid repetition of the return type:

std::istream_iterator<T> begin() {return {stream};}
std::istream_iterator<T> end() {return {};}

Answer 2

First of all, I would change the name to istream_range:

template<typename ValueType>
class istream_range

This will make it more in line with snake_case which standard uses, and is both cool sounding and descriptive. May be ValueType is a bit overkill, but I think that it makes it more clear clear that template parameter is for values.

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I think that range should be copyable. Input iterators are copyable too, but people know that it gets invalidated. It is usefull when chaining/pipelining/propagating. The only addition would be making stream a pointer and putting some dereferences.

I'm not sure which is the latest paper, but here is the quote from n4128:

We’ve already decided that Ranges (not Iterables) are copyable and assignable

The paper notes that there is an Iterable, but the title of the post says range.

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My opinion is that ranges should make user be able to do everything iterators can, but in a simpler and less verbose way. It would be core concept to keep in mind.

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std::istringstream would be better for example. It is more convenient, and gives reviewers more control.