upgraded to C++20

Author: fbourgin

src/Makevars

@@ -1,4 +1,4 @@
 ## -*- mode: makefile; -*-
 
-PKG_CXXFLAGS = -I../inst/include --std=c++17
+PKG_CXXFLAGS = -I../inst/include --std=c++20 -D_LIBCPP_DISABLE_AVAILABILITY
 # CXX_STD = CXX14

src/Makevars.win

@@ -1,4 +1,4 @@
 ## -*- mode: makefile; -*-
 
-PKG_CXXFLAGS = -I../inst/include --std=c++17
+PKG_CXXFLAGS = -I../inst/include --std=c++20
 # CXX_STD = CXX14

src/xtensor_r_example.cpp

@@ -8,7 +8,7 @@
 
 #include <Rcpp.h>
 
-// [[Rcpp::plugins(cpp17)]]
+// [[Rcpp::plugins(cpp20)]]
 
 // [[Rcpp::export]]
 xt::rtensor<double, 2> xtensor_r_example(xt::rtensor<int, 1> tens)