Namespaces
Variants

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

From cppreference.net
C++
Ranges library
Range adaptors
std::ranges::transform_view
Member functions
(C++26)
Deduction guides
Iterator
Sentinel
Defined in header <ranges>
(1)
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 >>
(since C++20)
(until C++23)
template < ranges:: input_range V,

std:: move_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 >>
(since C++23)
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) RangeAdaptorObject . 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.

Contents

Data members

Member Description
V base_ (private) the underlying view
( exposition-only member object* )
copyable-box <F> (until C++23) movable-box <F> (since C++23) fun_ (private) the underlying function object
( exposition-only member object* )

Member functions

constructs a transform_view
(public member function)
returns a copy of the underlying (adapted) view
(public member function)
returns an iterator to the beginning
(public member function)
returns an iterator or a sentinel to the end
(public member function)
returns the number of elements, provided only if the underlying (adapted) range satisfies sized_range
(public member function)
(C++26)
returns the approximate size of the resulting approximately_sized_range
(public member function)
Inherited from std::ranges::view_interface
returns whether the derived view is empty, provided only if it satisfies sized_range or forward_range
(public member function of std::ranges::view_interface<D> )
(C++23)
returns a constant iterator to the beginning of the range
(public member function of std::ranges::view_interface<D> )
(C++23)
returns a sentinel for the constant iterator of the range
(public member function of std::ranges::view_interface<D> )
returns whether the derived view is not empty, provided only if ranges::empty is applicable to it
(public member function of std::ranges::view_interface<D> )
returns the first element in the derived view, provided if it satisfies forward_range
(public member function of std::ranges::view_interface<D> )
returns the last element in the derived view, provided only if it satisfies bidirectional_range and common_range
(public member function of std::ranges::view_interface<D> )
returns the n th element in the derived view, provided only if it satisfies random_access_range
(public member function of std::ranges::view_interface<D> )

Deduction guides

Nested classes

the iterator type
( exposition-only member class template* )
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 ('Z' >= x and x >= 'A')
        return rot13a(x, 'A');
    if ('z' >= x and x >= 'a')
        return rot13a(x, 'a');
    return x;
}
int main()
{
    auto show = [](const unsigned char x) { std::putchar(x); };
    std::string in{"cppreference.net\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.net
pccersrerapr.pbz
pccersrerapr.pbz
cppreference.net

See also

(C++20)
applies a function to a range of elements
(algorithm function object)