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+---
+title: "basic_istream_view class (C++ Standard Library)| Microsoft Docs"
+description: "API reference for the Standard Template Library (STL) <ranges> basic_istream_view class, which reads (using operator>>) successive elements from an input stream."
+ms.date: 09/27/2022
+f1_keywords: ["ranges/std::basic_istream_view", "ranges/std::basic_istream_view::base", "ranges/std::basic_istream_view::begin", "ranges/std::basic_istream_view::data", "ranges/std::basic_istream_view::empty", "ranges/std::basic_istream_view::end", "ranges/std::basic_istream_view::size", "ranges/std::basic_istream_view::operator bool", "ranges/std::basic_istream_view::back", "ranges/std::basic_istream_view::front", "ranges/std::basic_istream_view::operator[]"]
+helpviewer_keywords: ["std::ranges::basic_istream_view [C++]", "std::ranges::basic_istream_view::base [C++]", "std::ranges::basic_istream_view::begin [C++]", "std::ranges::basic_istream_view::data [C++]", "std::ranges::basic_istream_view::empty [C++]", "std::ranges::basic_istream_view::end [C++]", "std::ranges::basic_istream_view::size [C++]", "std::ranges::basic_istream_view::back [C++]", "std::ranges::basic_istream_view::front [C++]", "std::ranges::basic_istream_view::operator[] [C++]", "std::ranges::basic_istream_view::operator bool [C++]"]
+dev_langs: ["C++"]
+---
+# `basic_istream_view` class (C++ Standard Library)
+
+A view of successive elements from an input stream.
+
+## Syntax
+
+```cpp
+template<movable Val, class CharT, class Traits>
+    requires default_initializable<Val> &&
+    stream_extractable <Val, CharT, Traits>
+class basic_istream_view : public view_interface<basic_istream_view<Val, CharT, Traits>>;
+```
+
+### Template parameters
+
+*`CharT`*\
+The character type of the stream.
+
+*`Traits`*\
+Optional. Provides details about the character type of the stream regarding comparing characters, determining the length of a string made up of that character type, and so on. An example trait is [`char_traits<wchar_t>`](char-traits-wchar-t-struct.md). If not specified, defaults to `char_traits<CharT>`.
+
+*`Val`*\
+The type of the elements to extract. For example, `double` given a stream of: `"1.1 2.2 3.3"`
+
+`stream_extractable` refers to the requirement (concept) that the type `Val` can be extracted from a stream using the `operator>>` function. It's equivalent to:
+
+```cpp
+template<class Val, class CharT, class Traits>
+concept stream_extractable =
+  requires(std::basic_istream<CharT,Traits>& is, Val& t) {
+    is >> t;
+  };
+```
+
+## View characteristics
+
+For a description of the following entries, see [View class characteristics](view-classes.md#view-classes-characteristics)
+
+| Characteristic | Description |
+|--|--|
+| **Range adaptor** | [`istream`](range-adaptors.md#istream) |
+| **Underlying range** | None  |
+| **Element type** |The same as `Val` |
+| **View iterator category** | `input_range` |
+| **Sized** | No |
+| **Is `const`-iterable** | No |
+| **Common range** | No |
+| **Borrowed range** | No |
+
+## Specializations
+
+Convenience alias templates are provided for `char` and `wchar_t` streams, as follows:
+
+```cpp
+1) template<class Val>
+using istream_view = ranges::basic_istream_view<Val, char>;
+
+2) template<class Val>
+using wistream_view = ranges::basic_istream_view<Val, wchar_t>;
+```
+
+1\) Reads elements from an input stream composed of `char` characters.\
+2\) Reads elements from an input stream composed of `wchar_t` characters.
+
+For 1) and 2), `Val` refers to the type of the elements to extract. For example, `double` given a stream of: `"1.1 2.2 3.3"`
+
+## Members
+
+| **Member functions** | **Description** |
+|--|--|
+| [Constructors](#constructors)<sup>C++20</sup> | Construct a `basic_istream_view`. |
+| [`begin`](#begin)<sup>C++20</sup> | Read the first value and get an iterator for the view. |
+| [`end`](#end)<sup>C++20</sup> | Returns `std::default_sentinel` |
+
+No member functions are inherited from `view_interface`.
+
+## Requirements
+
+**Header:** `<ranges>` (since C++ 20)
+
+**Namespace:** `std::ranges`
+
+**Compiler Option:** [`/std:c++20`](../build/reference/std-specify-language-standard-version.md) or later is required.
+
+## Constructors
+
+Construct an instance of a `basic_istream_view`.
+
+```cpp
+constexpr explicit
+basic_istream_view(std::basic_istream<CharT, Traits>& stream);
+```
+
+### Parameters
+
+*`stream`*\
+The stream to read from.
+
+For information about the template parameter type, see [Template parameters](#template-parameters).
+
+### Return value
+
+A `basic_istream_view` instance. The `basic_istream_view` internal stream pointer is initialized to  `addressof(stream)`.
+
+### Remarks
+
+The best way to create a `basic_istream_view` is by using the [`views::istream`](range-adaptors.md#istream) range adaptor. Range adaptors are the intended way to create view classes. The view types are exposed in case you want to create your own custom view type.
+
+### Example:  `basic_istream_view`
+
+```cpp
+// requires /std:c++20 or later
+#include <ranges>
+#include <iostream>
+#include <sstream>
+
+int main()
+{
+    // range adaptor
+    std::istringstream doubles{ "1.1 2.2 3.3 4.4 5.5" };
+    for (const auto& elem : std::views::istream<double>(doubles))
+    {
+        std::cout << elem << ' '; // 1.1 2.2 3.3 4.4 5.5
+    }
+    std::cout << '\n';
+
+    // istream_view alias
+    std::istringstream cpu1{ "8 0 8 0" };
+    // equivalent std::ranges::istream_view<int, char>
+    for (const auto& elem : std::ranges::istream_view<int>{cpu1})
+    {
+        std::cout << elem; // 8080
+    }
+    std::cout << '\n';
+    
+    // wistream_view alias
+    std::wistringstream cpu2{ L"6 5 0 2" };
+    // equivalent std::ranges::istream_view<int, wchar_t>
+    for (const auto& elem : std::ranges::wistream_view<int>{cpu2})
+    {
+        std::cout << elem; // 6502
+    }
+    std::cout << '\n';
+
+    // specify all template arguments
+    std::wistringstream misc(L"S T L");
+    std::ranges::basic_istream_view<wchar_t, wchar_t, std::char_traits<wchar_t>> basic{ misc };
+    for (const auto& elem : basic)
+    {
+        std::wcout << elem << ' '; // STL
+    }
+}
+```
+
+```output
+1.1 2.2 3.3 4.4 5.5
+8080
+6502
+S T L
+```
+
+## `begin`
+
+Read the first value and get an iterator to the view.
+
+```cpp
+constexpr auto begin();
+```
+
+### Parameters
+
+None.
+
+### Return value
+
+An iterator pointing at the first element in the `basic_istream_view`.
+
+## `end`
+
+Get the sentinel at the end of the view.
+
+```cpp
+constexpr std::default_sentinel_t end() const noexcept;
+```
+
+### Parameters
+
+None.
+
+### Return value
+
+`default_sentinel_t`
+
+## See also
+
+[`<ranges>`](ranges.md)\
+[View classes](view-classes.md)