NAME¶

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

Synopsis¶

Defined in header <ranges>
template< ranges::input_range V,

std::copy_constructible F >
requires ranges::view<V> &&
std::is_object_v<F> && (1) (since C++20)
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>>
namespace views {

inline constexpr /*unspecified*/ transform = /*unspecified*/; (2) (since C++20)

}
Call signature
template< ranges::viewable_range R, class F >

requires /* see below */ (since C++20)

constexpr ranges::view auto transform( R&& r, F&& fun );
template< class F > (since C++20)
constexpr /*range adaptor closure*/ transform( F&& fun );

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

Deduction guides

Nested classes

iterator the iterator type
(C++20) (exposition-only member class template)
sentinel the sentinel type
(C++20) (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 applies a function to a range of elements
(C++20) (niebloid)