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This adds constexpr to 11 algorithms defined in <numeric> as per P1645R1. 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 (__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.
file: libstdc++-v3/README New users may wish to point their web browsers to the file index.html in the 'doc/html' subdirectory. It contains brief building instructions and notes on how to configure the library in interesting ways.