std::ranges::views::transform, std::ranges::transform_view

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

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_value_t	range_reference_trange_rvalue_reference_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
Semiregular wrapper
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	views::counted
Adaptors
views::all_tviews::all join_viewviews::join take_viewviews::take basic_istream_viewistream_view	ref_view                                split_viewviews::split take_while_viewviews::take_while elements_viewviews::elements	common_viewviews::common transform_viewviews::transform drop_viewviews::drop keys_viewviews::keys	reverse_viewviews::reverse filter_viewviews::filter drop_while_viewviews::drop_while values_viewviews::values

 

std::ranges::transform_view

Member functions

transform_view::transform_view

transform_view::base

transform_view::begin

transform_view::end

transform_view::size

Deduction guides

Iterator

transform_view::iterator::iterator

transform_view::iterator::base

transform_view::iterator::operator*

transform_view::iterator::operator[]

transform_view::iterator::operator++ transform_view::iterator::operator++(int) transform_view::iterator::operator-- transform_view::iterator::operator--(int) transform_view::iterator::operator+= transform_view::iterator::operator-=

operator==(transform_view::iterator) operator<(transform_view::iterator) operator>(transform_view::iterator) operator<=(transform_view::iterator) operator>=(transform_view::iterator) operator<=>(transform_view::iterator)

operator+(transform_view::iterator) operator-(transform_view::iterator)

iter_move(transform_view::iterator)

iter_swap(transform_view::iterator)

Sentinel

transform_view::sentinel::sentinel

transform_view::sentinel::base

operator==(transform_view::iterator,transform_view::sentinel)

operator-(transform_view::iterator,transform_view::sentinel)

 

Defined in header <ranges>
template< ranges::input_range V,           std::copy_constructible F >   requires ranges::view<V> &&            std::is_object_v<F> &&            std::regular_invocable<F&, ranges::range_reference_t<V>> &&            /* invoke_result_t<F&, range_reference_t<V>>& is a valid type */ class transform_view : public ranges::view_interface<transform_view<V, F>>	(1)	(since C++20)
namespace views {     inline constexpr /*unspecified*/ transform = /*unspecified*/; }	(2)	(since C++20)

1) A range adaptor that represents view of an underlying sequence after applying a transformation function to each element.

2) Range adaptor object. The expression views::transform(E, F) is expression-equivalent to transform_view{E, F} for any suitable subexpressions E and F.

transform_view models the concepts random_access_range, bidirectional_range, forward_range, input_range, common_range, and sized_range when the underlying view V models respective concepts.

Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.

Member functions

(constructor)	constructs a transform_view (public member function)
base	returns a copy of the underlying (adapted) view (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
size	returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range (public member function)

Nested classes

iterator	the iterator type (public member class)
sentinel	the sentinel type (public member class)

Example

Run this code

#include <algorithm>
#include <array>
#include <cstdio>
#include <ranges>
#include <string>
 
class Transcoder {
    static constexpr std::array r{
        0x02,-0x02,-0x42, 0x05, 0x04, 0x05, 0x04,-0x02,
        0x00,-0x0a, 0x06,-0x04, 0x00, 0x0c, 0x03,-0x06,
    };
    decltype(r.size()) p{}, q{};
public:
    char operator() (int x) {
        ! (p|q)
        ? (99 == x ? x += r[p++]  : x -= r[q++])
        : (0 < p && p < r.size()) ? x += r[p++]
        : (0 < q && q < r.size()) ? x -= r[q++]
        : (0)
        ;
        return x;
    }
};
 
int main()
{
    auto show = [](const char x) { std::putchar(x); };
 
    std::string in{ "cppreference.com\n" };
    std::ranges::for_each(in, show);
 
    std::string out;
    std::ranges::copy(
        std::ranges::views::transform(in, Transcoder{}),
        std::back_inserter(out));
    std::ranges::for_each(out, show);
 
    auto view = std::ranges::transform_view{ out, Transcoder{} };
    std::ranges::for_each(view, show);
    std::ranges::for_each(view, show);
}

Output:

cppreference.com
en.wikipedia.org
cppreference.com
en.wikipedia.org

See also

ranges::transform (C++20)

applies a function to a range of elements (niebloid)