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libstdc++: P1645R1 constexpr for <numeric> algorithms

Message ID 20200225203611.1207978-1-ppalka@redhat.com
State New
Headers show
Series libstdc++: P1645R1 constexpr for <numeric> algorithms | expand

Commit Message

Patrick Palka Feb. 25, 2020, 8:36 p.m. UTC
This adds constexpr to 11 algorithms defined in <numeric> as per P1645R1.

Tested on x86_64-pc-linux-gnu, OK to commit?

libstdc++-v3/ChangeLog:

	P1645R1 constexpr for <numeric> algorithms
	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
	partial_sum, adjacent_difference): Make conditionally constexpr for
	C++20.
	* include/std/numeric (reduce, transform_reduce, exclusive_scan,
	inclusive_scan, transform_exclusive_scan, transform_inclusive_scan):
	Likewise.  Define the feature test macro __cpp_lib_constexpr_numeric.
	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc: Likewise.
	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc: Likewise.
	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.
---
 libstdc++-v3/include/bits/stl_numeric.h       |  9 +++
 libstdc++-v3/include/std/numeric              | 18 ++++++
 .../26_numerics/accumulate/constexpr.cc       | 42 ++++++++++++++
 .../adjacent_difference/constexpr.cc          | 44 +++++++++++++++
 .../26_numerics/exclusive_scan/constexpr.cc   | 44 +++++++++++++++
 .../26_numerics/inclusive_scan/constexpr.cc   | 55 +++++++++++++++++++
 .../26_numerics/inner_product/constexpr.cc    | 45 +++++++++++++++
 .../testsuite/26_numerics/iota/constexpr.cc   | 31 +++++++++++
 .../26_numerics/partial_sum/constexpr.cc      | 44 +++++++++++++++
 .../testsuite/26_numerics/reduce/constexpr.cc | 52 ++++++++++++++++++
 .../transform_exclusive_scan/constexpr.cc     | 33 +++++++++++
 .../transform_inclusive_scan/constexpr.cc     | 44 +++++++++++++++
 .../26_numerics/transform_reduce/constexpr.cc | 55 +++++++++++++++++++
 13 files changed, 516 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc

Comments

Jonathan Wakely Feb. 26, 2020, 2:29 p.m. UTC | #1
On 25/02/20 15:36 -0500, Patrick Palka wrote:
>This adds constexpr to 11 algorithms defined in <numeric> as per P1645R1.
>
>Tested on x86_64-pc-linux-gnu, OK to commit?
>
>libstdc++-v3/ChangeLog:
>
>	P1645R1 constexpr for <numeric> algorithms
>	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
>	partial_sum, adjacent_difference): Make conditionally constexpr for
>	C++20.
>	* include/std/numeric (reduce, transform_reduce, exclusive_scan,
>	inclusive_scan, transform_exclusive_scan, transform_inclusive_scan):
>	Likewise.  Define the feature test macro __cpp_lib_constexpr_numeric.
>	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
>	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
>	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
>	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
>	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
>	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
>	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
>	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
>	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc: Likewise.
>	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc: Likewise.
>	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.
>---
> libstdc++-v3/include/bits/stl_numeric.h       |  9 +++
> libstdc++-v3/include/std/numeric              | 18 ++++++
> .../26_numerics/accumulate/constexpr.cc       | 42 ++++++++++++++
> .../adjacent_difference/constexpr.cc          | 44 +++++++++++++++
> .../26_numerics/exclusive_scan/constexpr.cc   | 44 +++++++++++++++
> .../26_numerics/inclusive_scan/constexpr.cc   | 55 +++++++++++++++++++
> .../26_numerics/inner_product/constexpr.cc    | 45 +++++++++++++++
> .../testsuite/26_numerics/iota/constexpr.cc   | 31 +++++++++++
> .../26_numerics/partial_sum/constexpr.cc      | 44 +++++++++++++++
> .../testsuite/26_numerics/reduce/constexpr.cc | 52 ++++++++++++++++++
> .../transform_exclusive_scan/constexpr.cc     | 33 +++++++++++
> .../transform_inclusive_scan/constexpr.cc     | 44 +++++++++++++++
> .../26_numerics/transform_reduce/constexpr.cc | 55 +++++++++++++++++++
> 13 files changed, 516 insertions(+)
> create mode 100644 libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
> create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc
>
>diff --git a/libstdc++-v3/include/bits/stl_numeric.h b/libstdc++-v3/include/bits/stl_numeric.h
>index dd4683fe92e..f95c86a0d48 100644
>--- a/libstdc++-v3/include/bits/stl_numeric.h
>+++ b/libstdc++-v3/include/bits/stl_numeric.h
>@@ -83,6 +83,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  @ingroup numeric_ops
>    */
>   template<typename _ForwardIterator, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     void
>     iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value)
>     {
>@@ -128,6 +129,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    *  @return  The final sum.
>    */
>   template<typename _InputIterator, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     inline _Tp
>     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init)
>     {
>@@ -154,6 +156,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    *  @return  The final sum.
>    */
>   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     inline _Tp
>     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init,
> 	       _BinaryOperation __binary_op)
>@@ -182,6 +185,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    *  @return  The final inner product.
>    */
>   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     inline _Tp
>     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
> 		  _InputIterator2 __first2, _Tp __init)
>@@ -214,6 +218,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    */
>   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
> 	   typename _BinaryOperation1, typename _BinaryOperation2>
>+    _GLIBCXX20_CONSTEXPR
>     inline _Tp
>     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
> 		  _InputIterator2 __first2, _Tp __init,
>@@ -246,6 +251,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    *  @return  Iterator pointing just beyond the values written to __result.
>    */
>   template<typename _InputIterator, typename _OutputIterator>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     partial_sum(_InputIterator __first, _InputIterator __last,
> 		_OutputIterator __result)
>@@ -287,6 +293,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    */
>   template<typename _InputIterator, typename _OutputIterator,
> 	   typename _BinaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     partial_sum(_InputIterator __first, _InputIterator __last,
> 		_OutputIterator __result, _BinaryOperation __binary_op)
>@@ -326,6 +333,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    *  DR 539. partial_sum and adjacent_difference should mention requirements
>    */
>   template<typename _InputIterator, typename _OutputIterator>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     adjacent_difference(_InputIterator __first,
> 			_InputIterator __last, _OutputIterator __result)
>@@ -369,6 +377,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
>    */
>   template<typename _InputIterator, typename _OutputIterator,
> 	   typename _BinaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     adjacent_difference(_InputIterator __first, _InputIterator __last,
> 			_OutputIterator __result, _BinaryOperation __binary_op)
>diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric
>index cf35191cb47..8a7830ffd85 100644
>--- a/libstdc++-v3/include/std/numeric
>+++ b/libstdc++-v3/include/std/numeric
>@@ -249,6 +249,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  arithmetic) the result can be different.
>    */
>   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _Tp
>     reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
> 	   _BinaryOperation __binary_op)
>@@ -284,6 +285,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  Equivalent to calling `std::reduce(first, last, init, std::plus<>())`.
>    */
>   template<typename _InputIterator, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     inline _Tp
>     reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
>     { return std::reduce(__first, __last, std::move(__init), plus<>()); }
>@@ -300,6 +302,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  Equivalent to calling `std::reduce(first, last, T{}, std::plus<>())`.
>    */
>   template<typename _InputIterator>
>+    _GLIBCXX20_CONSTEXPR
>     inline typename iterator_traits<_InputIterator>::value_type
>     reduce(_InputIterator __first, _InputIterator __last)
>     {
>@@ -327,6 +330,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
> 	   typename _BinaryOperation1, typename _BinaryOperation2>
>+    _GLIBCXX20_CONSTEXPR
>     _Tp
>     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
> 		     _InputIterator2 __first2, _Tp __init,
>@@ -369,6 +373,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  elements.
>    */
>   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     inline _Tp
>     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
> 		     _InputIterator2 __first2, _Tp __init)
>@@ -394,6 +399,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _Tp,
> 	   typename _BinaryOperation, typename _UnaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _Tp
>     transform_reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
> 		     _BinaryOperation __binary_op, _UnaryOperation __unary_op)
>@@ -436,6 +442,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
> 	   typename _BinaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     exclusive_scan(_InputIterator __first, _InputIterator __last,
> 		   _OutputIterator __result, _Tp __init,
>@@ -469,6 +476,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  so the Nth input element is not included.
>    */
>   template<typename _InputIterator, typename _OutputIterator, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     inline _OutputIterator
>     exclusive_scan(_InputIterator __first, _InputIterator __last,
> 		   _OutputIterator __result, _Tp __init)
>@@ -497,6 +505,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _OutputIterator,
> 	   typename _BinaryOperation, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     inclusive_scan(_InputIterator __first, _InputIterator __last,
> 		   _OutputIterator __result, _BinaryOperation __binary_op,
>@@ -525,6 +534,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _OutputIterator,
> 	   typename _BinaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     inclusive_scan(_InputIterator __first, _InputIterator __last,
> 		   _OutputIterator __result, _BinaryOperation __binary_op)
>@@ -557,6 +567,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    *  so the Nth input element is included.
>    */
>   template<typename _InputIterator, typename _OutputIterator>
>+    _GLIBCXX20_CONSTEXPR
>     inline _OutputIterator
>     inclusive_scan(_InputIterator __first, _InputIterator __last,
> 		   _OutputIterator __result)
>@@ -584,6 +595,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
> 	   typename _BinaryOperation, typename _UnaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     transform_exclusive_scan(_InputIterator __first, _InputIterator __last,
> 			     _OutputIterator __result, _Tp __init,
>@@ -622,6 +634,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _OutputIterator,
> 	   typename _BinaryOperation, typename _UnaryOperation, typename _Tp>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
> 			     _OutputIterator __result,
>@@ -655,6 +668,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>    */
>   template<typename _InputIterator, typename _OutputIterator,
> 	  typename _BinaryOperation, typename _UnaryOperation>
>+    _GLIBCXX20_CONSTEXPR
>     _OutputIterator
>     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
> 			     _OutputIterator __result,
>@@ -676,6 +690,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>   // @} group numeric_ops
>
>+#if __cplusplus > 201703L
>+#define __cpp_lib_constexpr_numeric 201911L
>+#endif

Please put this before the algos rather than after them, and please
also add it to <version> (in the _GLIBCXX_HOSTED section for C++20
macros).

OK for master with those changes.
Patrick Palka Feb. 26, 2020, 3:28 p.m. UTC | #2
On Wed, 26 Feb 2020, Jonathan Wakely wrote:

> On 25/02/20 15:36 -0500, Patrick Palka wrote:
> > This adds constexpr to 11 algorithms defined in <numeric> as per P1645R1.
> > 
> > Tested on x86_64-pc-linux-gnu, OK to commit?
> > 
> > libstdc++-v3/ChangeLog:
> > 
> > 	P1645R1 constexpr for <numeric> algorithms
> > 	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
> > 	partial_sum, adjacent_difference): Make conditionally constexpr for
> > 	C++20.
> > 	* include/std/numeric (reduce, transform_reduce, exclusive_scan,
> > 	inclusive_scan, transform_exclusive_scan, transform_inclusive_scan):
> > 	Likewise.  Define the feature test macro __cpp_lib_constexpr_numeric.
> > 	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
> > 	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
> > 	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc:
> > Likewise.
> > 	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc:
> > Likewise.
> > 	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.
> > ---
> > libstdc++-v3/include/bits/stl_numeric.h       |  9 +++
> > libstdc++-v3/include/std/numeric              | 18 ++++++
> > .../26_numerics/accumulate/constexpr.cc       | 42 ++++++++++++++
> > .../adjacent_difference/constexpr.cc          | 44 +++++++++++++++
> > .../26_numerics/exclusive_scan/constexpr.cc   | 44 +++++++++++++++
> > .../26_numerics/inclusive_scan/constexpr.cc   | 55 +++++++++++++++++++
> > .../26_numerics/inner_product/constexpr.cc    | 45 +++++++++++++++
> > .../testsuite/26_numerics/iota/constexpr.cc   | 31 +++++++++++
> > .../26_numerics/partial_sum/constexpr.cc      | 44 +++++++++++++++
> > .../testsuite/26_numerics/reduce/constexpr.cc | 52 ++++++++++++++++++
> > .../transform_exclusive_scan/constexpr.cc     | 33 +++++++++++
> > .../transform_inclusive_scan/constexpr.cc     | 44 +++++++++++++++
> > .../26_numerics/transform_reduce/constexpr.cc | 55 +++++++++++++++++++
> > 13 files changed, 516 insertions(+)
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
> > create mode 100644 libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
> > create mode 100644 libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
> > create mode 100644
> > libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc
> > 
> > diff --git a/libstdc++-v3/include/bits/stl_numeric.h
> > b/libstdc++-v3/include/bits/stl_numeric.h
> > index dd4683fe92e..f95c86a0d48 100644
> > --- a/libstdc++-v3/include/bits/stl_numeric.h
> > +++ b/libstdc++-v3/include/bits/stl_numeric.h
> > @@ -83,6 +83,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  @ingroup numeric_ops
> >    */
> >   template<typename _ForwardIterator, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     void
> >     iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value)
> >     {
> > @@ -128,6 +129,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    *  @return  The final sum.
> >    */
> >   template<typename _InputIterator, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _Tp
> >     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init)
> >     {
> > @@ -154,6 +156,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    *  @return  The final sum.
> >    */
> >   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _Tp
> >     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init,
> > 	       _BinaryOperation __binary_op)
> > @@ -182,6 +185,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    *  @return  The final inner product.
> >    */
> >   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _Tp
> >     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
> > 		  _InputIterator2 __first2, _Tp __init)
> > @@ -214,6 +218,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    */
> >   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
> > 	   typename _BinaryOperation1, typename _BinaryOperation2>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _Tp
> >     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
> > 		  _InputIterator2 __first2, _Tp __init,
> > @@ -246,6 +251,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    *  @return  Iterator pointing just beyond the values written to __result.
> >    */
> >   template<typename _InputIterator, typename _OutputIterator>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     partial_sum(_InputIterator __first, _InputIterator __last,
> > 		_OutputIterator __result)
> > @@ -287,6 +293,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    */
> >   template<typename _InputIterator, typename _OutputIterator,
> > 	   typename _BinaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     partial_sum(_InputIterator __first, _InputIterator __last,
> > 		_OutputIterator __result, _BinaryOperation __binary_op)
> > @@ -326,6 +333,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    *  DR 539. partial_sum and adjacent_difference should mention
> > requirements
> >    */
> >   template<typename _InputIterator, typename _OutputIterator>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     adjacent_difference(_InputIterator __first,
> > 			_InputIterator __last, _OutputIterator __result)
> > @@ -369,6 +377,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
> >    */
> >   template<typename _InputIterator, typename _OutputIterator,
> > 	   typename _BinaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     adjacent_difference(_InputIterator __first, _InputIterator __last,
> > 			_OutputIterator __result, _BinaryOperation
> > __binary_op)
> > diff --git a/libstdc++-v3/include/std/numeric
> > b/libstdc++-v3/include/std/numeric
> > index cf35191cb47..8a7830ffd85 100644
> > --- a/libstdc++-v3/include/std/numeric
> > +++ b/libstdc++-v3/include/std/numeric
> > @@ -249,6 +249,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  arithmetic) the result can be different.
> >    */
> >   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _Tp
> >     reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
> > 	   _BinaryOperation __binary_op)
> > @@ -284,6 +285,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  Equivalent to calling `std::reduce(first, last, init, std::plus<>())`.
> >    */
> >   template<typename _InputIterator, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _Tp
> >     reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
> >     { return std::reduce(__first, __last, std::move(__init), plus<>()); }
> > @@ -300,6 +302,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  Equivalent to calling `std::reduce(first, last, T{}, std::plus<>())`.
> >    */
> >   template<typename _InputIterator>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline typename iterator_traits<_InputIterator>::value_type
> >     reduce(_InputIterator __first, _InputIterator __last)
> >     {
> > @@ -327,6 +330,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
> > 	   typename _BinaryOperation1, typename _BinaryOperation2>
> > +    _GLIBCXX20_CONSTEXPR
> >     _Tp
> >     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
> > 		     _InputIterator2 __first2, _Tp __init,
> > @@ -369,6 +373,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  elements.
> >    */
> >   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _Tp
> >     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
> > 		     _InputIterator2 __first2, _Tp __init)
> > @@ -394,6 +399,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _Tp,
> > 	   typename _BinaryOperation, typename _UnaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _Tp
> >     transform_reduce(_InputIterator __first, _InputIterator __last, _Tp
> > __init,
> > 		     _BinaryOperation __binary_op, _UnaryOperation __unary_op)
> > @@ -436,6 +442,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
> > 	   typename _BinaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     exclusive_scan(_InputIterator __first, _InputIterator __last,
> > 		   _OutputIterator __result, _Tp __init,
> > @@ -469,6 +476,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  so the Nth input element is not included.
> >    */
> >   template<typename _InputIterator, typename _OutputIterator, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _OutputIterator
> >     exclusive_scan(_InputIterator __first, _InputIterator __last,
> > 		   _OutputIterator __result, _Tp __init)
> > @@ -497,6 +505,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _OutputIterator,
> > 	   typename _BinaryOperation, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     inclusive_scan(_InputIterator __first, _InputIterator __last,
> > 		   _OutputIterator __result, _BinaryOperation __binary_op,
> > @@ -525,6 +534,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _OutputIterator,
> > 	   typename _BinaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     inclusive_scan(_InputIterator __first, _InputIterator __last,
> > 		   _OutputIterator __result, _BinaryOperation __binary_op)
> > @@ -557,6 +567,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    *  so the Nth input element is included.
> >    */
> >   template<typename _InputIterator, typename _OutputIterator>
> > +    _GLIBCXX20_CONSTEXPR
> >     inline _OutputIterator
> >     inclusive_scan(_InputIterator __first, _InputIterator __last,
> > 		   _OutputIterator __result)
> > @@ -584,6 +595,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
> > 	   typename _BinaryOperation, typename _UnaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     transform_exclusive_scan(_InputIterator __first, _InputIterator __last,
> > 			     _OutputIterator __result, _Tp __init,
> > @@ -622,6 +634,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _OutputIterator,
> > 	   typename _BinaryOperation, typename _UnaryOperation, typename _Tp>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
> > 			     _OutputIterator __result,
> > @@ -655,6 +668,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >    */
> >   template<typename _InputIterator, typename _OutputIterator,
> > 	  typename _BinaryOperation, typename _UnaryOperation>
> > +    _GLIBCXX20_CONSTEXPR
> >     _OutputIterator
> >     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
> > 			     _OutputIterator __result,
> > @@ -676,6 +690,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > 
> >   // @} group numeric_ops
> > 
> > +#if __cplusplus > 201703L
> > +#define __cpp_lib_constexpr_numeric 201911L
> > +#endif
> 
> Please put this before the algos rather than after them, and please
> also add it to <version> (in the _GLIBCXX_HOSTED section for C++20
> macros).
> 
> OK for master with those changes.

Thanks for the review, here is what I committed:

---
 libstdc++-v3/ChangeLog                        | 24 ++++++++
 libstdc++-v3/include/bits/stl_numeric.h       |  9 +++
 libstdc++-v3/include/std/numeric              | 18 ++++++
 libstdc++-v3/include/std/version              |  1 +
 .../26_numerics/accumulate/constexpr.cc       | 42 ++++++++++++++
 .../adjacent_difference/constexpr.cc          | 44 +++++++++++++++
 .../26_numerics/exclusive_scan/constexpr.cc   | 44 +++++++++++++++
 .../26_numerics/inclusive_scan/constexpr.cc   | 55 +++++++++++++++++++
 .../26_numerics/inner_product/constexpr.cc    | 45 +++++++++++++++
 .../testsuite/26_numerics/iota/constexpr.cc   | 31 +++++++++++
 .../26_numerics/partial_sum/constexpr.cc      | 44 +++++++++++++++
 .../testsuite/26_numerics/reduce/constexpr.cc | 52 ++++++++++++++++++
 .../transform_exclusive_scan/constexpr.cc     | 33 +++++++++++
 .../transform_inclusive_scan/constexpr.cc     | 44 +++++++++++++++
 .../26_numerics/transform_reduce/constexpr.cc | 55 +++++++++++++++++++
 15 files changed, 541 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
 create mode 100644 libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index d545526d93a..8af27d4cc52 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,27 @@
+2020-02-26  Patrick Palka  <ppalka@redhat.com>
+
+	P1645R1 constexpr for <numeric> algorithms
+	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
+	partial_sum, adjacent_difference): Make conditionally constexpr for
+	C++20.
+	* include/std/numeric (__cpp_lib_constexpr_numeric): Define this feature
+	test macro.
+	(reduce, transform_reduce, exclusive_scan, inclusive_scan,
+	transform_exclusive_scan, transform_inclusive_scan): Make conditionally
+	constexpr for C++20.
+	* include/std/version (__cpp_lib_constexpr_numeric): Define.
+	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
+	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
+	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
+	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
+	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
+	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
+	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
+	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
+	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc: Likewise.
+	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc: Likewise.
+	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.
+
 2020-02-26  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/bits/ranges_algo.h (__lexicographical_compare_fn): Declare
diff --git a/libstdc++-v3/include/bits/stl_numeric.h b/libstdc++-v3/include/bits/stl_numeric.h
index dd4683fe92e..f95c86a0d48 100644
--- a/libstdc++-v3/include/bits/stl_numeric.h
+++ b/libstdc++-v3/include/bits/stl_numeric.h
@@ -83,6 +83,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  @ingroup numeric_ops
    */
   template<typename _ForwardIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     void
     iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value)
     {
@@ -128,6 +129,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  The final sum.
    */
   template<typename _InputIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init)
     {
@@ -154,6 +156,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  The final sum.
    */
   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init,
 	       _BinaryOperation __binary_op)
@@ -182,6 +185,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  The final inner product.
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
 		  _InputIterator2 __first2, _Tp __init)
@@ -214,6 +218,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
 	   typename _BinaryOperation1, typename _BinaryOperation2>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
 		  _InputIterator2 __first2, _Tp __init,
@@ -246,6 +251,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  Iterator pointing just beyond the values written to __result.
    */
   template<typename _InputIterator, typename _OutputIterator>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     partial_sum(_InputIterator __first, _InputIterator __last,
 		_OutputIterator __result)
@@ -287,6 +293,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     partial_sum(_InputIterator __first, _InputIterator __last,
 		_OutputIterator __result, _BinaryOperation __binary_op)
@@ -326,6 +333,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  DR 539. partial_sum and adjacent_difference should mention requirements
    */
   template<typename _InputIterator, typename _OutputIterator>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     adjacent_difference(_InputIterator __first,
 			_InputIterator __last, _OutputIterator __result)
@@ -369,6 +377,7 @@ _GLIBCXX_BEGIN_NAMESPACE_ALGO
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     adjacent_difference(_InputIterator __first, _InputIterator __last,
 			_OutputIterator __result, _BinaryOperation __binary_op)
diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric
index cf35191cb47..57dcac6d215 100644
--- a/libstdc++-v3/include/std/numeric
+++ b/libstdc++-v3/include/std/numeric
@@ -226,6 +226,10 @@ namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
+#if __cplusplus > 201703L
+#define __cpp_lib_constexpr_numeric 201911L
+#endif
+
   /// @addtogroup numeric_ops
   /// @{
 
@@ -249,6 +253,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  arithmetic) the result can be different.
    */
   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _Tp
     reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
 	   _BinaryOperation __binary_op)
@@ -284,6 +289,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  Equivalent to calling `std::reduce(first, last, init, std::plus<>())`.
    */
   template<typename _InputIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
     { return std::reduce(__first, __last, std::move(__init), plus<>()); }
@@ -300,6 +306,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  Equivalent to calling `std::reduce(first, last, T{}, std::plus<>())`.
    */
   template<typename _InputIterator>
+    _GLIBCXX20_CONSTEXPR
     inline typename iterator_traits<_InputIterator>::value_type
     reduce(_InputIterator __first, _InputIterator __last)
     {
@@ -327,6 +334,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
 	   typename _BinaryOperation1, typename _BinaryOperation2>
+    _GLIBCXX20_CONSTEXPR
     _Tp
     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
 		     _InputIterator2 __first2, _Tp __init,
@@ -369,6 +377,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  elements.
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
 		     _InputIterator2 __first2, _Tp __init)
@@ -394,6 +403,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _Tp,
 	   typename _BinaryOperation, typename _UnaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _Tp
     transform_reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
 		     _BinaryOperation __binary_op, _UnaryOperation __unary_op)
@@ -436,6 +446,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     exclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _Tp __init,
@@ -469,6 +480,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  so the Nth input element is not included.
    */
   template<typename _InputIterator, typename _OutputIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _OutputIterator
     exclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _Tp __init)
@@ -497,6 +509,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     inclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _BinaryOperation __binary_op,
@@ -525,6 +538,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     inclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _BinaryOperation __binary_op)
@@ -557,6 +571,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  so the Nth input element is included.
    */
   template<typename _InputIterator, typename _OutputIterator>
+    _GLIBCXX20_CONSTEXPR
     inline _OutputIterator
     inclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result)
@@ -584,6 +599,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
 	   typename _BinaryOperation, typename _UnaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     transform_exclusive_scan(_InputIterator __first, _InputIterator __last,
 			     _OutputIterator __result, _Tp __init,
@@ -622,6 +638,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation, typename _UnaryOperation, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
 			     _OutputIterator __result,
@@ -655,6 +672,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	  typename _BinaryOperation, typename _UnaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
 			     _OutputIterator __result,
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index e2ccf619d4a..c6a202e250d 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -187,6 +187,7 @@
 #define __cpp_lib_constexpr_complex 201711L
 #define __cpp_lib_constexpr_dynamic_alloc 201907L
 #define __cpp_lib_constexpr_invoke 201907L
+#define __cpp_lib_constexpr_numeric 201911L
 #define __cpp_lib_erase_if 202002L
 #define __cpp_lib_interpolate 201902L
 #ifdef _GLIBCXX_HAS_GTHREADS
diff --git a/libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
new file mode 100644
index 00000000000..6fefd5a3f98
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
@@ -0,0 +1,42 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  auto sum = std::accumulate(x, x+5, 0);
+  return sum == 15;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  auto prod = std::accumulate(x, x+5, 1, std::multiplies{});
+  return prod == 120;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
new file mode 100644
index 00000000000..5f79284e268
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5];
+  std::adjacent_difference(x, x+5, y);
+  return y[0] == 1 && y[1] == 1 && y[2] == 1 && y[3] == 1 && y[4] == 1;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5];
+  std::adjacent_difference(x, x+5, y, std::multiplies{});
+  return y[0] == 1 && y[1] == 2 && y[2] == 6 && y[3] == 12 && y[4] == 20;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..c885ba5dbd1
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::exclusive_scan(x, x+3, y, 0);
+  return y[0] == 0 && y[1] == 1 && y[2] == 3;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::exclusive_scan(x, x+3, y, 1, std::multiplies{});
+  return y[0] == 1 && y[1] == 1 && y[2] == 2;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..a50a70e9fc2
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
@@ -0,0 +1,55 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::inclusive_scan(x, x+3, y);
+  return y[0] == 1 && y[1] == 3 && y[2] == 6;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::inclusive_scan(x, x+3, y, std::multiplies{});
+  return y[0] == 1 && y[1] == 2 && y[2] == 6;
+}
+
+static_assert(test02());
+
+constexpr bool
+test03()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::inclusive_scan(x, x+3, y, std::multiplies{}, 2);
+  return y[0] == 2 && y[1] == 4 && y[2] == 12;
+}
+
+static_assert(test03());
diff --git a/libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
new file mode 100644
index 00000000000..a6aaf351560
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
@@ -0,0 +1,45 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::inner_product(x, x+5, y, 0);
+  return ret == 110;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::inner_product(x, x+5, y, 1,
+				std::multiplies{}, std::plus{});
+  return ret == 3*6*9*12*15;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
new file mode 100644
index 00000000000..50eecf8b605
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
@@ -0,0 +1,31 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {0};
+  std::iota(x, x+3, 0);
+  return x[0] == 0 && x[1] == 1 && x[2] == 2;
+}
+
+static_assert(test01());
diff --git a/libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
new file mode 100644
index 00000000000..c2e758492e4
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::partial_sum(x, x+3, y);
+  return y[0] == 1 && y[1] == 3 && y[2] == 6;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::partial_sum(x, x+3, y, std::multiplies{});
+  return y[0] == 1 && y[1] == 2 && y[2] == 6;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
new file mode 100644
index 00000000000..5ed48892df2
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
@@ -0,0 +1,52 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  auto sum = std::reduce(x, x+5);
+  return sum == 15;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  auto sum = std::reduce(x, x+5, 0);
+  return sum == 15;
+}
+
+static_assert(test02());
+
+constexpr bool
+test03()
+{
+  int x[5] = {1,2,3,4,5};
+  auto prod = std::reduce(x, x+5, 1, std::multiplies{});
+  return prod == 120;
+}
+
+static_assert(test03());
diff --git a/libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..f01fd241a8a
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
@@ -0,0 +1,33 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::transform_exclusive_scan(x, x+3, y, 0, std::plus{}, std::negate{});
+  return y[0] == 0 && y[1] == -1 && y[2] == -3;
+}
+
+static_assert(test01());
diff --git a/libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..6f072b74569
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
@@ -0,0 +1,44 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::transform_inclusive_scan(x, x+3, y, std::plus{}, std::negate{}, 0);
+  return y[0] == -1 && y[1] == -3 && y[2] == -6;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::transform_inclusive_scan(x, x+3, y, std::plus{}, std::negate{});
+  return y[0] == -1 && y[1] == -3 && y[2] == -6;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc
new file mode 100644
index 00000000000..eb054c1f8af
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc
@@ -0,0 +1,55 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::transform_reduce(x, x+5, y, 0);
+  return ret == 110;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::transform_reduce(x, x+5, y, 1,
+				   std::multiplies{}, std::plus{});
+  return ret == 3*6*9*12*15;
+}
+
+static_assert(test02());
+
+constexpr bool
+test03()
+{
+  int x[5] = {1,2,3,4,5};
+  auto ret = std::transform_reduce(x, x+5, 0, std::plus{}, std::negate{});
+  return ret == -15;
+}
+
+static_assert(test03());
Jonathan Wakely Feb. 28, 2020, 5:14 p.m. UTC | #3
On 26/02/20 10:28 -0500, Patrick Palka wrote:
>On Wed, 26 Feb 2020, Jonathan Wakely wrote:
>
>> On 25/02/20 15:36 -0500, Patrick Palka wrote:
>> > This adds constexpr to 11 algorithms defined in <numeric> as per P1645R1.
>> >
>> > Tested on x86_64-pc-linux-gnu, OK to commit?
>> >
>> > libstdc++-v3/ChangeLog:
>> >
>> > 	P1645R1 constexpr for <numeric> algorithms
>> > 	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
>> > 	partial_sum, adjacent_difference): Make conditionally constexpr for
>> > 	C++20.
>> > 	* include/std/numeric (reduce, transform_reduce, exclusive_scan,
>> > 	inclusive_scan, transform_exclusive_scan, transform_inclusive_scan):
>> > 	Likewise.  Define the feature test macro __cpp_lib_constexpr_numeric.
>> > 	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
>> > 	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
>> > 	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc:
>> > Likewise.
>> > 	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc:
>> > Likewise.
>> > 	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.

testsuite/26_numerics/headers/numeric/synopsis.cc is now failing when
run with -std=gnu++2a.

For testsuite/25_algorithms/headers/algorithm/synopsis.cc we just
added _GLIBCXX20_CONSTEXPR to the test as needed.
Patrick Palka Feb. 28, 2020, 5:57 p.m. UTC | #4
On Fri, 28 Feb 2020, Jonathan Wakely wrote:

> On 26/02/20 10:28 -0500, Patrick Palka wrote:
> > On Wed, 26 Feb 2020, Jonathan Wakely wrote:
> > 
> > > On 25/02/20 15:36 -0500, Patrick Palka wrote:
> > > > This adds constexpr to 11 algorithms defined in <numeric> as per
> > > P1645R1.
> > > >
> > > > Tested on x86_64-pc-linux-gnu, OK to commit?
> > > >
> > > > libstdc++-v3/ChangeLog:
> > > >
> > > > 	P1645R1 constexpr for <numeric> algorithms
> > > > 	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
> > > > 	partial_sum, adjacent_difference): Make conditionally constexpr for
> > > > 	C++20.
> > > > 	* include/std/numeric (reduce, transform_reduce, exclusive_scan,
> > > > 	inclusive_scan, transform_exclusive_scan, transform_inclusive_scan):
> > > > 	Likewise.  Define the feature test macro __cpp_lib_constexpr_numeric.
> > > > 	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
> > > > 	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
> > > > 	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc:
> > > > Likewise.
> > > > 	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc:
> > > > Likewise.
> > > > 	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.
> 
> testsuite/26_numerics/headers/numeric/synopsis.cc is now failing when
> run with -std=gnu++2a.
> 
> For testsuite/25_algorithms/headers/algorithm/synopsis.cc we just
> added _GLIBCXX20_CONSTEXPR to the test as needed.

Does this look OK to commit?

-- >8 --

Subject: [PATCH] libstdc++: Update the <numeric> synopsis test to latest
 standard

Tested with

  make check RUNTESTFLAGS="conformance.exp=*numeric*synopsis* --target_board=unix/-std=$std"

for std in {c++98, c++11, c++17, c++2a}.

libstdc++-v3/ChangeLog:

	* testsuite/26_numerics/headers/numeric/synopsis.cc: Add signatures for
	functions introduced in C++11, C++17 and C++2a.  Add 'constexpr' to
	existing signatures for C++2a.
---
 .../26_numerics/headers/numeric/synopsis.cc   | 111 ++++++++++++++++++
 1 file changed, 111 insertions(+)

diff --git a/libstdc++-v3/testsuite/26_numerics/headers/numeric/synopsis.cc b/libstdc++-v3/testsuite/26_numerics/headers/numeric/synopsis.cc
index 8d3850ff0cf..5a9465c45f4 100644
--- a/libstdc++-v3/testsuite/26_numerics/headers/numeric/synopsis.cc
+++ b/libstdc++-v3/testsuite/26_numerics/headers/numeric/synopsis.cc
@@ -19,46 +19,157 @@
 
 #include <numeric>
 
+#if __cplusplus > 201703L
+#define CONSTEXPR constexpr
+#else
+#define CONSTEXPR
+#endif
+
 namespace std {
   template <class InputIterator, class T>
+    CONSTEXPR
     T accumulate(InputIterator first, InputIterator last, T init);
 
   template <class InputIterator, class T, class BinaryOperation>
+    CONSTEXPR
     T accumulate(InputIterator first, InputIterator last, T init,
                  BinaryOperation binary_op);
 
   template <class InputIterator1, class InputIterator2, class T>
+    CONSTEXPR
     T inner_product(InputIterator1 first1, InputIterator1 last1,
                     InputIterator2 first2, T init);
 
   template <class InputIterator1, class InputIterator2, class T,
             class BinaryOperation1, class BinaryOperation2>
+    CONSTEXPR
     T inner_product(InputIterator1 first1, InputIterator1 last1,
                     InputIterator2 first2, T init,
                     BinaryOperation1 binary_op1,
                     BinaryOperation2 binary_op2);
 
   template <class InputIterator, class OutputIterator>
+    CONSTEXPR
     OutputIterator partial_sum(InputIterator first,
                                InputIterator last,
                                OutputIterator result);
 
   template <class InputIterator, class OutputIterator,
             class BinaryOperation>
+    CONSTEXPR
     OutputIterator partial_sum(InputIterator first,
                                InputIterator last,
                                OutputIterator result,
                                BinaryOperation binary_op);
 
   template <class InputIterator, class OutputIterator>
+    CONSTEXPR
     OutputIterator adjacent_difference(InputIterator first,
                                        InputIterator last,
                                        OutputIterator result);
 
   template <class InputIterator, class OutputIterator,
             class BinaryOperation>
+    CONSTEXPR
     OutputIterator adjacent_difference(InputIterator first,
                                        InputIterator last,
                                        OutputIterator result,
                                        BinaryOperation binary_op);
+#if __cplusplus >= 201103L
+  template<class ForwardIterator, class T>
+    CONSTEXPR void iota(ForwardIterator first, ForwardIterator last, T value);
+#endif // C++11
+
+#if __cplusplus >= 201703L
+  template<class InputIterator>
+    CONSTEXPR typename iterator_traits<InputIterator>::value_type
+    reduce(InputIterator first, InputIterator last);
+
+  template<class InputIterator, class T>
+    CONSTEXPR T reduce(InputIterator first, InputIterator last, T init);
+
+  template<class InputIterator, class T, class BinaryOperation>
+    CONSTEXPR T reduce(InputIterator first, InputIterator last, T init,
+		       BinaryOperation binary_op);
+
+  template<class InputIterator, class OutputIterator, class T>
+    CONSTEXPR OutputIterator
+    exclusive_scan(InputIterator first, InputIterator last,
+		   OutputIterator result, T init);
+
+  template<class InputIterator, class OutputIterator, class T,
+	   class BinaryOperation>
+    CONSTEXPR OutputIterator
+    exclusive_scan(InputIterator first, InputIterator last,
+		   OutputIterator result, T init, BinaryOperation binary_op);
+
+  template<class InputIterator, class OutputIterator>
+    CONSTEXPR OutputIterator
+    inclusive_scan(InputIterator first, InputIterator last,
+		   OutputIterator result);
+
+  template<class InputIterator, class OutputIterator, class BinaryOperation>
+    CONSTEXPR OutputIterator
+    inclusive_scan(InputIterator first, InputIterator last,
+		   OutputIterator result, BinaryOperation binary_op);
+
+  template<class InputIterator, class OutputIterator, class BinaryOperation,
+	   class T>
+    CONSTEXPR OutputIterator
+    inclusive_scan(InputIterator first, InputIterator last,
+		   OutputIterator result, BinaryOperation binary_op, T init);
+
+  template<class InputIterator1, class InputIterator2, class T>
+    CONSTEXPR T transform_reduce(InputIterator1 first1, InputIterator1 last1,
+				 InputIterator2 first2, T init);
+
+  template<class InputIterator1, class InputIterator2, class T,
+	   class BinaryOperation1, class BinaryOperation2>
+    CONSTEXPR T transform_reduce(InputIterator1 first1, InputIterator1 last1,
+				 InputIterator2 first2, T init,
+				 BinaryOperation1 binary_op1,
+				 BinaryOperation2 binary_op2);
+
+  template<class InputIterator, class T,
+	   class BinaryOperation, class UnaryOperation>
+    CONSTEXPR T transform_reduce(InputIterator first, InputIterator last, T init,
+				 BinaryOperation binary_op,
+				 UnaryOperation unary_op);
+
+  template<class InputIterator, class OutputIterator, class T,
+	   class BinaryOperation, class UnaryOperation>
+    CONSTEXPR OutputIterator
+    transform_exclusive_scan(InputIterator first, InputIterator last,
+			     OutputIterator result, T init,
+			     BinaryOperation binary_op, UnaryOperation unary_op);
+
+  template<class InputIterator, class OutputIterator,
+	   class BinaryOperation, class UnaryOperation>
+    CONSTEXPR OutputIterator
+    transform_inclusive_scan(InputIterator first, InputIterator last,
+			     OutputIterator result,
+			     BinaryOperation binary_op, UnaryOperation unary_op);
+
+  template<class InputIterator, class OutputIterator,
+	   class BinaryOperation, class UnaryOperation, class T>
+    CONSTEXPR OutputIterator
+    transform_inclusive_scan(InputIterator first, InputIterator last,
+			     OutputIterator result,
+			     BinaryOperation binary_op, UnaryOperation unary_op,
+			     T init);
+#endif // C++17
+
+#if __cplusplus > 201703L
+  template<class M, class N>
+    constexpr common_type_t<M,N> gcd(M m, N n);
+
+  template<class M, class N>
+    constexpr common_type_t<M,N> lcm(M m, N n);
+
+  template<class T>
+    constexpr T midpoint(T a, T b) noexcept;
+
+  template<class T>
+    constexpr T* midpoint(T* a, T* b);
+#endif // C++2a
 }
Jonathan Wakely Feb. 28, 2020, 6:19 p.m. UTC | #5
On 28/02/20 12:57 -0500, Patrick Palka wrote:
>On Fri, 28 Feb 2020, Jonathan Wakely wrote:
>
>> On 26/02/20 10:28 -0500, Patrick Palka wrote:
>> > On Wed, 26 Feb 2020, Jonathan Wakely wrote:
>> >
>> > > On 25/02/20 15:36 -0500, Patrick Palka wrote:
>> > > > This adds constexpr to 11 algorithms defined in <numeric> as per
>> > > P1645R1.
>> > > >
>> > > > Tested on x86_64-pc-linux-gnu, OK to commit?
>> > > >
>> > > > libstdc++-v3/ChangeLog:
>> > > >
>> > > > 	P1645R1 constexpr for <numeric> algorithms
>> > > > 	* include/bits/stl_numeric.h (iota, accumulate, inner_product,
>> > > > 	partial_sum, adjacent_difference): Make conditionally constexpr for
>> > > > 	C++20.
>> > > > 	* include/std/numeric (reduce, transform_reduce, exclusive_scan,
>> > > > 	inclusive_scan, transform_exclusive_scan, transform_inclusive_scan):
>> > > > 	Likewise.  Define the feature test macro __cpp_lib_constexpr_numeric.
>> > > > 	* testsuite/26_numerics/accumulate/constexpr.cc: New test.
>> > > > 	* testsuite/26_numerics/adjacent_difference/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/exclusive_scan/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/inclusive_scan/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/inner_product/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/iota/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/partial_sum/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/reduce/constexpr.cc: Likewise.
>> > > > 	* testsuite/26_numerics/transform_exclusive_scan/constexpr.cc:
>> > > > Likewise.
>> > > > 	* testsuite/26_numerics/transform_inclusive_scan/constexpr.cc:
>> > > > Likewise.
>> > > > 	* testsuite/26_numerics/transform_reduce/constexpr.cc: Likewise.
>>
>> testsuite/26_numerics/headers/numeric/synopsis.cc is now failing when
>> run with -std=gnu++2a.
>>
>> For testsuite/25_algorithms/headers/algorithm/synopsis.cc we just
>> added _GLIBCXX20_CONSTEXPR to the test as needed.
>
>Does this look OK to commit?

Yes, thanks.
diff mbox series

Patch

diff --git a/libstdc++-v3/include/bits/stl_numeric.h b/libstdc++-v3/include/bits/stl_numeric.h
index dd4683fe92e..f95c86a0d48 100644
--- a/libstdc++-v3/include/bits/stl_numeric.h
+++ b/libstdc++-v3/include/bits/stl_numeric.h
@@ -83,6 +83,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  @ingroup numeric_ops
    */
   template<typename _ForwardIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     void
     iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value)
     {
@@ -128,6 +129,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  The final sum.
    */
   template<typename _InputIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init)
     {
@@ -154,6 +156,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  The final sum.
    */
   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     accumulate(_InputIterator __first, _InputIterator __last, _Tp __init,
 	       _BinaryOperation __binary_op)
@@ -182,6 +185,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  The final inner product.
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
 		  _InputIterator2 __first2, _Tp __init)
@@ -214,6 +218,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
 	   typename _BinaryOperation1, typename _BinaryOperation2>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     inner_product(_InputIterator1 __first1, _InputIterator1 __last1,
 		  _InputIterator2 __first2, _Tp __init,
@@ -246,6 +251,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  @return  Iterator pointing just beyond the values written to __result.
    */
   template<typename _InputIterator, typename _OutputIterator>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     partial_sum(_InputIterator __first, _InputIterator __last,
 		_OutputIterator __result)
@@ -287,6 +293,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     partial_sum(_InputIterator __first, _InputIterator __last,
 		_OutputIterator __result, _BinaryOperation __binary_op)
@@ -326,6 +333,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    *  DR 539. partial_sum and adjacent_difference should mention requirements
    */
   template<typename _InputIterator, typename _OutputIterator>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     adjacent_difference(_InputIterator __first,
 			_InputIterator __last, _OutputIterator __result)
@@ -369,6 +377,7 @@  _GLIBCXX_BEGIN_NAMESPACE_ALGO
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     adjacent_difference(_InputIterator __first, _InputIterator __last,
 			_OutputIterator __result, _BinaryOperation __binary_op)
diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric
index cf35191cb47..8a7830ffd85 100644
--- a/libstdc++-v3/include/std/numeric
+++ b/libstdc++-v3/include/std/numeric
@@ -249,6 +249,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  arithmetic) the result can be different.
    */
   template<typename _InputIterator, typename _Tp, typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _Tp
     reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
 	   _BinaryOperation __binary_op)
@@ -284,6 +285,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  Equivalent to calling `std::reduce(first, last, init, std::plus<>())`.
    */
   template<typename _InputIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
     { return std::reduce(__first, __last, std::move(__init), plus<>()); }
@@ -300,6 +302,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  Equivalent to calling `std::reduce(first, last, T{}, std::plus<>())`.
    */
   template<typename _InputIterator>
+    _GLIBCXX20_CONSTEXPR
     inline typename iterator_traits<_InputIterator>::value_type
     reduce(_InputIterator __first, _InputIterator __last)
     {
@@ -327,6 +330,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp,
 	   typename _BinaryOperation1, typename _BinaryOperation2>
+    _GLIBCXX20_CONSTEXPR
     _Tp
     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
 		     _InputIterator2 __first2, _Tp __init,
@@ -369,6 +373,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  elements.
    */
   template<typename _InputIterator1, typename _InputIterator2, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _Tp
     transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
 		     _InputIterator2 __first2, _Tp __init)
@@ -394,6 +399,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _Tp,
 	   typename _BinaryOperation, typename _UnaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _Tp
     transform_reduce(_InputIterator __first, _InputIterator __last, _Tp __init,
 		     _BinaryOperation __binary_op, _UnaryOperation __unary_op)
@@ -436,6 +442,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     exclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _Tp __init,
@@ -469,6 +476,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  so the Nth input element is not included.
    */
   template<typename _InputIterator, typename _OutputIterator, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     inline _OutputIterator
     exclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _Tp __init)
@@ -497,6 +505,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     inclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _BinaryOperation __binary_op,
@@ -525,6 +534,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     inclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result, _BinaryOperation __binary_op)
@@ -557,6 +567,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  so the Nth input element is included.
    */
   template<typename _InputIterator, typename _OutputIterator>
+    _GLIBCXX20_CONSTEXPR
     inline _OutputIterator
     inclusive_scan(_InputIterator __first, _InputIterator __last,
 		   _OutputIterator __result)
@@ -584,6 +595,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator, typename _Tp,
 	   typename _BinaryOperation, typename _UnaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     transform_exclusive_scan(_InputIterator __first, _InputIterator __last,
 			     _OutputIterator __result, _Tp __init,
@@ -622,6 +634,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	   typename _BinaryOperation, typename _UnaryOperation, typename _Tp>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
 			     _OutputIterator __result,
@@ -655,6 +668,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
    */
   template<typename _InputIterator, typename _OutputIterator,
 	  typename _BinaryOperation, typename _UnaryOperation>
+    _GLIBCXX20_CONSTEXPR
     _OutputIterator
     transform_inclusive_scan(_InputIterator __first, _InputIterator __last,
 			     _OutputIterator __result,
@@ -676,6 +690,10 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   // @} group numeric_ops
 
+#if __cplusplus > 201703L
+#define __cpp_lib_constexpr_numeric 201911L
+#endif
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
diff --git a/libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
new file mode 100644
index 00000000000..6fefd5a3f98
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/accumulate/constexpr.cc
@@ -0,0 +1,42 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  auto sum = std::accumulate(x, x+5, 0);
+  return sum == 15;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  auto prod = std::accumulate(x, x+5, 1, std::multiplies{});
+  return prod == 120;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
new file mode 100644
index 00000000000..5f79284e268
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/adjacent_difference/constexpr.cc
@@ -0,0 +1,44 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5];
+  std::adjacent_difference(x, x+5, y);
+  return y[0] == 1 && y[1] == 1 && y[2] == 1 && y[3] == 1 && y[4] == 1;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5];
+  std::adjacent_difference(x, x+5, y, std::multiplies{});
+  return y[0] == 1 && y[1] == 2 && y[2] == 6 && y[3] == 12 && y[4] == 20;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..c885ba5dbd1
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/exclusive_scan/constexpr.cc
@@ -0,0 +1,44 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::exclusive_scan(x, x+3, y, 0);
+  return y[0] == 0 && y[1] == 1 && y[2] == 3;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::exclusive_scan(x, x+3, y, 1, std::multiplies{});
+  return y[0] == 1 && y[1] == 1 && y[2] == 2;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..a50a70e9fc2
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/inclusive_scan/constexpr.cc
@@ -0,0 +1,55 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::inclusive_scan(x, x+3, y);
+  return y[0] == 1 && y[1] == 3 && y[2] == 6;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::inclusive_scan(x, x+3, y, std::multiplies{});
+  return y[0] == 1 && y[1] == 2 && y[2] == 6;
+}
+
+static_assert(test02());
+
+constexpr bool
+test03()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::inclusive_scan(x, x+3, y, std::multiplies{}, 2);
+  return y[0] == 2 && y[1] == 4 && y[2] == 12;
+}
+
+static_assert(test03());
diff --git a/libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
new file mode 100644
index 00000000000..a6aaf351560
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/inner_product/constexpr.cc
@@ -0,0 +1,45 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::inner_product(x, x+5, y, 0);
+  return ret == 110;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::inner_product(x, x+5, y, 1,
+				std::multiplies{}, std::plus{});
+  return ret == 3*6*9*12*15;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
new file mode 100644
index 00000000000..50eecf8b605
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/iota/constexpr.cc
@@ -0,0 +1,31 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {0};
+  std::iota(x, x+3, 0);
+  return x[0] == 0 && x[1] == 1 && x[2] == 2;
+}
+
+static_assert(test01());
diff --git a/libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
new file mode 100644
index 00000000000..c2e758492e4
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/partial_sum/constexpr.cc
@@ -0,0 +1,44 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::partial_sum(x, x+3, y);
+  return y[0] == 1 && y[1] == 3 && y[2] == 6;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::partial_sum(x, x+3, y, std::multiplies{});
+  return y[0] == 1 && y[1] == 2 && y[2] == 6;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
new file mode 100644
index 00000000000..5ed48892df2
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/reduce/constexpr.cc
@@ -0,0 +1,52 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  auto sum = std::reduce(x, x+5);
+  return sum == 15;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  auto sum = std::reduce(x, x+5, 0);
+  return sum == 15;
+}
+
+static_assert(test02());
+
+constexpr bool
+test03()
+{
+  int x[5] = {1,2,3,4,5};
+  auto prod = std::reduce(x, x+5, 1, std::multiplies{});
+  return prod == 120;
+}
+
+static_assert(test03());
diff --git a/libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..f01fd241a8a
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/transform_exclusive_scan/constexpr.cc
@@ -0,0 +1,33 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::transform_exclusive_scan(x, x+3, y, 0, std::plus{}, std::negate{});
+  return y[0] == 0 && y[1] == -1 && y[2] == -3;
+}
+
+static_assert(test01());
diff --git a/libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
new file mode 100644
index 00000000000..6f072b74569
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/transform_inclusive_scan/constexpr.cc
@@ -0,0 +1,44 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::transform_inclusive_scan(x, x+3, y, std::plus{}, std::negate{}, 0);
+  return y[0] == -1 && y[1] == -3 && y[2] == -6;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[3] = {1,2,3};
+  int y[3];
+  std::transform_inclusive_scan(x, x+3, y, std::plus{}, std::negate{});
+  return y[0] == -1 && y[1] == -3 && y[2] == -6;
+}
+
+static_assert(test02());
diff --git a/libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc
new file mode 100644
index 00000000000..eb054c1f8af
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/transform_reduce/constexpr.cc
@@ -0,0 +1,55 @@ 
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+#include <numeric>
+
+constexpr bool
+test01()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::transform_reduce(x, x+5, y, 0);
+  return ret == 110;
+}
+
+static_assert(test01());
+
+constexpr bool
+test02()
+{
+  int x[5] = {1,2,3,4,5};
+  int y[5] = {2,4,6,8,10};
+  auto ret = std::transform_reduce(x, x+5, y, 1,
+				   std::multiplies{}, std::plus{});
+  return ret == 3*6*9*12*15;
+}
+
+static_assert(test02());
+
+constexpr bool
+test03()
+{
+  int x[5] = {1,2,3,4,5};
+  auto ret = std::transform_reduce(x, x+5, 0, std::plus{}, std::negate{});
+  return ret == -15;
+}
+
+static_assert(test03());