std::ranges::basic_istream_view, std::ranges::istream_view

 

C++

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Feature test macros (C++20)

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Ranges library (C++20)

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Technical specifications

Symbols index

External libraries

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range primitives
iterator_tsentinel_t	range_size_trange_difference_t	range_reference_trange_rvalue_reference_t	range_value_t
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	basic_istream_viewistream_view
Adaptors
views::all_tviews::all common_viewviews::common filter_viewviews::filter reverse_viewviews::reverse	take_viewviews::take take_while_viewviews::take_while drop_viewviews::drop drop_while_viewviews::drop_while	elements_viewviews::elements keys_viewviews::keys values_viewviews::values transform_viewviews::transform	join_viewviews::join split_viewviews::split lazy_split_viewviews::lazy_split ref_view views::counted
Range adaptor objects
Range adaptor closure objects
Helper items
copyable-box	simple-view

 

std::ranges::basic_istream_view

Member functions

basic_istream_view::basic_istream_view (C++20)

basic_istream_view::begin (C++20)

basic_istream_view::end (C++20)

Iterator

basic_istream_view::iterator::iterator (C++20)

basic_istream_view::iterator::operator= (C++20)

basic_istream_view::iterator::operator++ (C++20)

basic_istream_view::iterator::operator* (C++20)

operator==(basic_istream_view::iterator) (C++20)

 

Defined in header <ranges>
template< std::movable Val, class CharT, class Traits = std::char_traits<CharT> >   requires std::default_initializable<Val> &&            /*stream-extractable*/<Val,CharT,Traits> class basic_istream_view     : public ranges::view_interface<basic_istream_view<Val,CharT,Traits>>	(1)	(since C++20)
template< class Val, class CharT, class Traits > ranges::basic_istream_view<Val,CharT,Traits>     istream_view( std::basic_istream<CharT,Traits>& s );	(2)	(since C++20)
Helper concepts
template< class Val, class CharT, class Traits > concept /*stream-extractable*/ =   requires(std::basic_istream<CharT,Traits>& is, Val& t) {     is >> t;   };	(3)	(since C++20)

1) A range factory that generates a sequence of elements by repeatedly calling operator>>.

2) Returns a basic_istream_view, deducing CharT and Traits from s. Equivalent to return basic_istream_view<Val, CharT, Traits>{s};.

3) The exposition-only concept /*stream-extractable*/<Val,CharT,Traits> is satisfied when lvalue of Val can be extracted from lvalue of std::basic_istream<CharT,Traits>.

The iterator type of basic_istream_view is move-only: it does not meet the LegacyIterator requirements, and thus does not work with pre-C++20 algorithms.

Member functions

(constructor) (C++20)	constructs a basic_istream_view (public member function)
begin (C++20)	returns an iterator (public member function)
end (C++20)	returns std::default_sentinel (public member function)
Inherited from std::ranges::view_interface
(none)	Although basic_istream_view is derived from std::ranges::view_interface, it cannot use any of inherited member functions.

std::ranges::basic_istream_view::basic_istream_view

constexpr explicit     basic_istream_view( std::basic_istream<CharT, Traits>& stream );		(since C++20)

Initializes the stored pointer to stream with std::addressof(stream), and value-initializes the stored value of Val.

std::ranges::basic_istream_view::begin

constexpr auto begin();		(since C++20)

Equivalent to *stream_ >> value_; return /*iterator*/{*this};, where stream_ is the stored pointer to stream and value_ is the stored value of Val.

std::ranges::basic_istream_view::end

constexpr std::default_sentinel_t end() const noexcept;		(since C++20)

Equivalent to return std::default_sentinel;.

Nested classes

iterator (C++20)

the iterator type of basic_istream_view, the name is exposition-only (exposition-only member class)

Example

Run this code

#include <algorithm>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <ranges>
#include <sstream>
#include <string>
 
int main()
{
    auto words = std::istringstream{"today is yesterday’s tomorrow"};
    for (const auto& s: std::ranges::istream_view<std::string>(words)) {
        std::cout << std::quoted(s, '/') << ' ';
    }
    std::cout << '\n';
 
    auto floats = std::istringstream{"1.1  2.2\t3.3\v4.4\f55\n66\r7.7  8.8"};
    std::ranges::copy(
        std::ranges::istream_view<float>(floats),
        std::ostream_iterator<float>{std::cout, ", "});
    std::cout << '\n';
}

Output:

/today/ /is/ /yesterday’s/ /tomorrow/
1.1, 2.2, 3.3, 4.4, 55, 66, 7.7, 8.8,

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P2325R3	C++20	default constructor was provided as view must be default_initializable	removed along with the requirement

See also

istream_iterator

input iterator that reads from std::basic_istream (class template)