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std::experimental::ranges:: projected

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C++
Experimental
Ranges
Iterators library
Iterator concepts
Indirect callable concepts
Common algorithm requirements
Concept utilities
projected
Iterator utilities and operations
Iterator traits
Iterator adaptors
Stream iterators
template < Readable I, IndirectRegularUnaryInvocable < I > Proj >

struct projected {
using value_type =
std:: remove_cv_t < std:: remove_reference_t < ranges :: indirect_result_of_t < Proj & ( I ) >>> ;
ranges :: indirect_result_of_t < Proj & ( I ) > operator * ( ) const ;
} ;

template < WeaklyIncrementable I, class Proj >
struct difference_type < projected < I, Proj >> {
using type = ranges :: difference_type_t < I > ;

} ;
(ranges TS)

The class template projected bundles a Readable type I and a function Proj into a new Readable type whose reference type is the result of applying Proj to the reference type of I . It exists solely to ease constraint specification, and so its operator * ( ) may not be actually defined.