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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General 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)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range conversions
to (C++23)
Range primitives
range_size_trange_difference_t range_value_t	range_reference_trange_const_reference_trange_rvalue_reference_t   (C++23)	iterator_tconst_iterator_tsentinel_t (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range    sized_range constant_range (C++23)	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 iota_viewviews::iota	single_viewviews::single basic_istream_viewviews::istream	repeat_viewviews::repeat (C++23)(C++23)
Adaptors
ref_view views::all_tviews::all common_viewviews::common owning_view views::counted reverse_viewviews::reverse zip_viewviews::zip (C++23)(C++23) as_const_viewviews::as_const (C++23)(C++23) as_rvalue_viewviews::as_rvalue (C++23)(C++23)	take_viewviews::take take_while_viewviews::take_while drop_viewviews::drop drop_while_viewviews::drop_while zip_transform_viewviews::zip_transform (C++23)(C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23)   cartesian_product_viewviews::cartesian_product (C++23)(C++23)	elements_viewviews::elements keys_viewviews::keys values_viewviews::values transform_viewviews::transform adjacent_viewviews::adjacent (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) stride_viewviews::stride (C++23)(C++23)	filter_viewviews::filter join_viewviews::join split_viewviews::split lazy_split_viewviews::lazy_split join_with_viewviews::join_with (C++23)(C++23) chunk_viewviews::chunk (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23)
Range adaptor objects
Range adaptor closure objects
Helper items
copyable-box	simple-view

 

std::ranges::transform_view

Member functions

transform_view::transform_view (C++20)

transform_view::base (C++20)

transform_view::begin (C++20)

transform_view::end (C++20)

transform_view::size (C++20)

Deduction guides

Iterator

transform_view::iterator::iterator (C++20)

transform_view::iterator::base (C++20)

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

transform_view::iterator::operator[] (C++20)

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-= (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

operator==(transform_view::iterator) operator<(transform_view::iterator) operator>(transform_view::iterator) operator<=(transform_view::iterator) operator>=(transform_view::iterator) operator<=>(transform_view::iterator) (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

operator+(transform_view::iterator) operator-(transform_view::iterator) (C++20)(C++20)

iter_move(transform_view::iterator) (C++20)

Sentinel

transform_view::sentinel::sentinel (C++20)

transform_view::sentinel::base (C++20)

operator==(transform_view::iterator,transform_view::sentinel) (C++20)

operator-(transform_view::iterator,transform_view::sentinel) (C++20)

 

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)
Call signature
template< ranges::viewable_range R, class F >     requires /* see below */ constexpr ranges::view auto transform( R&& r, F&& fun );		(since C++20)
template< class F > constexpr /*range adaptor closure*/ transform( F&& fun );		(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, and
• either both are constant subexpressions or else neither is a constant subexpression, and
• either both are potentially-throwing or else neither is potentially-throwing (i.e. noexcept(e) == noexcept(f)).

Member functions

(constructor) (C++20)	constructs a transform_view (public member function)
base (C++20)	returns a copy of the underlying (adapted) view (public member function)
begin (C++20)	returns an iterator to the beginning (public member function)
end (C++20)	returns an iterator or a sentinel to the end (public member function)
size (C++20)	returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range. (public member function)
Inherited from std::ranges::view_interface
empty (C++20)	Returns whether the derived view is empty. Provided if it satisfies sized_range or forward_range. (public member function of std::ranges::view_interface<D>)
operator bool (C++20)	Returns whether the derived view is not empty. Provided if ranges::empty is applicable to it. (public member function of std::ranges::view_interface<D>)
front (C++20)	Returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>)
back (C++20)	Returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range. (public member function of std::ranges::view_interface<D>)
operator[] (C++20)	Returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>)

Nested classes

iterator (C++20)	the iterator type (exposition-only member class template)
sentinel (C++20)	the sentinel type (exposition-only member class template)

Example

Run this code

#include <algorithm>
#include <cstdio>
#include <iterator>
#include <ranges>
#include <string>
 
char rot13a(const char x, const char a)
{
    return a + (x - a + 13) % 26;
}
 
char rot13(const char x)
{
    if (x >= 'A' && x <= 'Z') {
        return rot13a(x, 'A');
    }
 
    if (x >= 'a' && x <= 'z') {
        return rot13a(x, 'a');
    }
 
    return x;
}
 
int main()
{
    auto show = [](const unsigned char x) { std::putchar(x); };
 
    std::string in{ "cppreference.com\n" };
    std::ranges::for_each(in, show);
    std::ranges::for_each(in | std::views::transform(rot13), show);
 
    std::string out;
    std::ranges::copy( std::views::transform(in, rot13), std::back_inserter(out) );
    std::ranges::for_each(out, show);
    std::ranges::for_each(out | std::views::transform(rot13), show);
}

Output:

cppreference.com
pccersrerapr.pbz
pccersrerapr.pbz
cppreference.com

See also

ranges::transform (C++20)

applies a function to a range of elements (niebloid)