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Mar 8, 2023
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[LWG 8] P2609R3 Relaxing Ranges Just A Smidge #6137

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P2609R3 Relaxing Ranges Just A Smidge
burblebee Feb 18, 2023
7119853
[indirectcallable.traits] Clarify template vs specialization
burblebee Mar 1, 2023
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48 changes: 33 additions & 15 deletions source/iterators.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -84,9 +84,12 @@
template<class In>
concept indirectly_readable = @\seebelow@; // freestanding

template<@\libconcept{indirectly_readable}@ T>
using @\exposidnc{indirect-value-t}@ = @\seebelow@; // \expos

template<@\libconcept{indirectly_readable}@ T>
using @\libglobal{iter_common_reference_t}@ = // freestanding
common_reference_t<iter_reference_t<T>, iter_value_t<T>&>;
common_reference_t<iter_reference_t<T>, @\exposid{indirect-value-t}@<T>>;

// \ref{iterator.concept.writable}, concept \libconcept{indirectly_writable}
template<class Out, class T>
Expand Down Expand Up @@ -2411,6 +2414,21 @@
There are several concepts that group requirements of algorithms that
take callable objects\iref{func.def} as arguments.

\rSec3[indirectcallable.traits]{Indirect callable traits}

\pnum
To implement algorithms taking projections,
it is necessary to determine the projected type of an iterator's value type.
For the exposition-only alias template \exposid{indirect-value-t},
\tcode{\exposid{indirect-value-t}<T>} denotes
\begin{itemize}
\item
\tcode{invoke_result_t<Proj\&, \exposid{indirect-value-t}<I>>}
if \tcode{T} names \tcode{projected<I, Proj>}, and
\item
\tcode{iter_value_t<T>\&} otherwise.
\end{itemize}

\rSec3[indirectcallable.indirectinvocable]{Indirect callables}

\pnum
Expand All @@ -2423,59 +2441,59 @@
concept @\deflibconcept{indirectly_unary_invocable}@ =
@\libconcept{indirectly_readable}@<I> &&
@\libconcept{copy_constructible}@<F> &&
@\libconcept{invocable}@<F&, iter_value_t<I>&> &&
@\libconcept{invocable}@<F&, @\exposid{indirect-value-t}@<I>> &&
@\libconcept{invocable}@<F&, iter_reference_t<I>> &&
@\libconcept{invocable}@<F&, iter_common_reference_t<I>> &&
@\libconcept{common_reference_with}@<
invoke_result_t<F&, iter_value_t<I>&>,
invoke_result_t<F&, @\exposid{indirect-value-t}@<I>>,
invoke_result_t<F&, iter_reference_t<I>>>;

template<class F, class I>
concept @\deflibconcept{indirectly_regular_unary_invocable}@ =
@\libconcept{indirectly_readable}@<I> &&
@\libconcept{copy_constructible}@<F> &&
@\libconcept{regular_invocable}@<F&, iter_value_t<I>&> &&
@\libconcept{regular_invocable}@<F&, @\exposid{indirect-value-t}@<I>> &&
@\libconcept{regular_invocable}@<F&, iter_reference_t<I>> &&
@\libconcept{regular_invocable}@<F&, iter_common_reference_t<I>> &&
@\libconcept{common_reference_with}@<
invoke_result_t<F&, iter_value_t<I>&>,
invoke_result_t<F&, @\exposid{indirect-value-t}@<I>>,
invoke_result_t<F&, iter_reference_t<I>>>;

template<class F, class I>
concept @\deflibconcept{indirect_unary_predicate}@ =
@\libconcept{indirectly_readable}@<I> &&
@\libconcept{copy_constructible}@<F> &&
@\libconcept{predicate}@<F&, iter_value_t<I>&> &&
@\libconcept{predicate}@<F&, @\exposid{indirect-value-t}@<I>> &&
@\libconcept{predicate}@<F&, iter_reference_t<I>> &&
@\libconcept{predicate}@<F&, iter_common_reference_t<I>>;

template<class F, class I1, class I2>
concept @\deflibconcept{indirect_binary_predicate}@ =
@\libconcept{indirectly_readable}@<I1> && @\libconcept{indirectly_readable}@<I2> &&
@\libconcept{copy_constructible}@<F> &&
@\libconcept{predicate}@<F&, iter_value_t<I1>&, iter_value_t<I2>&> &&
@\libconcept{predicate}@<F&, iter_value_t<I1>&, iter_reference_t<I2>> &&
@\libconcept{predicate}@<F&, iter_reference_t<I1>, iter_value_t<I2>&> &&
@\libconcept{predicate}@<F&, @\exposid{indirect-value-t}@<I1>, @\exposid{indirect-value-t}@<I2>> &&
@\libconcept{predicate}@<F&, @\exposid{indirect-value-t}@<I1>, iter_reference_t<I2>> &&
@\libconcept{predicate}@<F&, iter_reference_t<I1>, @\exposid{indirect-value-t}@<I2>> &&
@\libconcept{predicate}@<F&, iter_reference_t<I1>, iter_reference_t<I2>> &&
@\libconcept{predicate}@<F&, iter_common_reference_t<I1>, iter_common_reference_t<I2>>;

template<class F, class I1, class I2 = I1>
concept @\deflibconcept{indirect_equivalence_relation}@ =
@\libconcept{indirectly_readable}@<I1> && @\libconcept{indirectly_readable}@<I2> &&
@\libconcept{copy_constructible}@<F> &&
@\libconcept{equivalence_relation}@<F&, iter_value_t<I1>&, iter_value_t<I2>&> &&
@\libconcept{equivalence_relation}@<F&, iter_value_t<I1>&, iter_reference_t<I2>> &&
@\libconcept{equivalence_relation}@<F&, iter_reference_t<I1>, iter_value_t<I2>&> &&
@\libconcept{equivalence_relation}@<F&, @\exposid{indirect-value-t}@<I1>, @\exposid{indirect-value-t}@<I2>> &&
@\libconcept{equivalence_relation}@<F&, @\exposid{indirect-value-t}@<I1>, iter_reference_t<I2>> &&
@\libconcept{equivalence_relation}@<F&, iter_reference_t<I1>, @\exposid{indirect-value-t}@<I2>&> &&
@\libconcept{equivalence_relation}@<F&, iter_reference_t<I1>, iter_reference_t<I2>> &&
@\libconcept{equivalence_relation}@<F&, iter_common_reference_t<I1>, iter_common_reference_t<I2>>;

template<class F, class I1, class I2 = I1>
concept @\deflibconcept{indirect_strict_weak_order}@ =
@\libconcept{indirectly_readable}@<I1> && @\libconcept{indirectly_readable}@<I2> &&
@\libconcept{copy_constructible}@<F> &&
@\libconcept{strict_weak_order}@<F&, iter_value_t<I1>&, iter_value_t<I2>&> &&
@\libconcept{strict_weak_order}@<F&, iter_value_t<I1>&, iter_reference_t<I2>> &&
@\libconcept{strict_weak_order}@<F&, iter_reference_t<I1>, iter_value_t<I2>&> &&
@\libconcept{strict_weak_order}@<F&, @\exposid{indirect-value-t}@<I1>, @\exposid{indirect-value-t}@<I2>> &&
@\libconcept{strict_weak_order}@<F&, @\exposid{indirect-value-t}@<I1>, iter_reference_t<I2>> &&
@\libconcept{strict_weak_order}@<F&, iter_reference_t<I1>, @\exposid{indirect-value-t}@<I2>> &&
@\libconcept{strict_weak_order}@<F&, iter_reference_t<I1>, iter_reference_t<I2>> &&
@\libconcept{strict_weak_order}@<F&, iter_common_reference_t<I1>, iter_common_reference_t<I2>>;
}
Expand Down
2 changes: 1 addition & 1 deletion source/support.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -682,7 +682,7 @@
#define @\defnlibxname{cpp_lib_polymorphic_allocator}@ 201902L // also in \libheader{memory_resource}
#define @\defnlibxname{cpp_lib_print}@ 202207L // also in \libheader{print}, \libheader{ostream}
#define @\defnlibxname{cpp_lib_quoted_string_io}@ 201304L // also in \libheader{iomanip}
#define @\defnlibxname{cpp_lib_ranges}@ 202211L
#define @\defnlibxname{cpp_lib_ranges}@ 202302L
// also in \libheader{algorithm}, \libheader{functional}, \libheader{iterator}, \libheader{memory}, \libheader{ranges}
#define @\defnlibxname{cpp_lib_ranges_as_const}@ 202207L // also in \libheader{ranges}
#define @\defnlibxname{cpp_lib_ranges_as_rvalue}@ 202207L // also in \libheader{ranges}
Expand Down