Replies: 3 comments 17 replies
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It may help to step back. 'Plain old scalar' types like Otherwise what you do in your post seems roughly correct. The |
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Much appreciated. Then I assume the above just worked "by accident" and isn't intended behaviour. |
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Yep I would agree 😆 I think it is purely stylistic, and the end of the day we have to give the compiler something it can work with. I just played a little with this via > cppFunction("arma::mat foo(Nullable<NumericMatrix> m) { NumericMatrix nm{m}; arma::mat am{Rcpp::as<arma::mat>(nm)}; return am; }", depends="RcppArmadillo")
> cppFunction("arma::mat foo(Nullable<NumericMatrix> m) { NumericMatrix nm{m}; arma::mat am{Rcpp::as<arma::mat>(m)}; return am; }", depends="RcppArmadillo")
> cppFunction("arma::mat foo(Nullable<NumericMatrix> m) { arma::mat am{Rcpp::as<arma::mat>(m)}; return am; }", depends="RcppArmadillo") |
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Actually, come to think about it, "by accident" is not right. These will likely invoke the same templating via > cppFunction("void foo(Nullable<double> s) { if (s.isNotNull()) { double d = as<double>(s); } }")
> In case like this is can be illuminating to look at either one of the unit tests (not much here) or within CRAN if the search is good and we see that PS And even more for |
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So a fuller answer may be: supports all types for we have |
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For Armadillo matrices, you can use a small lambda expression, initialise with arma advanced ctor, and invoke it immediately: cppFunction("
arma::mat foo(Nullable<NumericMatrix> m = R_NilValue) {
const arma::mat& x = [&m] {
if (m.isNotNull()) {
NumericMatrix M(m);
arma::mat x(M.begin(), M.nrow(), M.ncol(), false, true); // copy_aux_mem is set to false, no copying
return x;
} else {
arma::mat x(0, 0, arma::fill::none);
return x;
}
}(); // invoke!
return x;
}
/*** R
foo(m = NULL)
foo(m = matrix(1:4, ncol = 2))
*/
", depends="RcppArmadillo")From R console: foo()
<0 x 0 matrix>
foo(matrix(1:4, ncol = 2))
[,1] [,2]
[1,] 1 3
[2,] 2 4 |
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And it does. So nice. We don't even need the Code#include <RcppArmadillo/Lightest>
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
arma::mat foo(Rcpp::Nullable<Rcpp::NumericMatrix> m = R_NilValue) {
const arma::mat& x = [&m] {
if (m.isNotNull()) {
Rcpp::NumericMatrix M(m);
arma::mat x(M.begin(), M.nrow(), M.ncol(), false, true); // adv ctor, no copying
return x;
} else {
arma::mat x(0, 0, arma::fill::none);
return x;
}
}(); // invoke!
return x;
}
// [[Rcpp::export]]
arma::mat bar(Rcpp::Nullable<arma::mat> m = R_NilValue) {
const arma::mat& x = [&m] {
if (m.isNotNull()) {
return m.as();
} else {
return arma::mat{0, 0, arma::fill::none};
}
}(); // invoke!
return x;
}
// [[Rcpp::export]]
arma::mat bis(Rcpp::Nullable<arma::mat> m = R_NilValue) {
return (m.isNotNull() ? m.as() : arma::mat{0, 0, arma::fill::none});
}
/*** R
foo(NULL)
foo(matrix(1:4, ncol = 2))
bar()
bar(matrix(1:4, ncol = 2))
bis()
bis(matrix(1:4, ncol = 2))
*/Demo> Rcpp::sourceCpp("arma_nullable_example.cpp")
> foo(NULL)
<0 x 0 matrix>
> foo(matrix(1:4, ncol = 2))
[,1] [,2]
[1,] 1 3
[2,] 2 4
> bar()
<0 x 0 matrix>
> bar(matrix(1:4, ncol = 2))
[,1] [,2]
[1,] 1 3
[2,] 2 4
> bis()
<0 x 0 matrix>
> bis(matrix(1:4, ncol = 2))
[,1] [,2]
[1,] 1 3
[2,] 2 4
> |
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Just a note, #include <RcppArmadillo/Lightest>
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
arma::mat foo(Rcpp::Nullable<Rcpp::NumericMatrix> m = R_NilValue) {
const arma::mat& x = [&m] {
if (m.isNotNull()) {
Rcpp::NumericMatrix M(m);
arma::mat x(M.begin(), M.nrow(), M.ncol(), false, true); // adv ctor, no copying
return x += 1;
} else {
arma::mat x(0, 0, arma::fill::none);
return x;
}
}(); // invoke!
return x;
}
// [[Rcpp::export]]
arma::mat bis(Rcpp::Nullable<arma::mat> m = R_NilValue) {
return (m.isNotNull() ? m.as() += 1: arma::mat{0, 0, arma::fill::none});
}
/*** R
# Pass by reference
x1 <- matrix(rep(1, 4), ncol = 2)
foo(x1)
cat("x1 after: ")
x1
# Pass by value
x2 <- matrix(rep(1, 4), ncol = 2)
bis(x2)
cat("x2 after: ")
x2
*/
> # Pass by reference
> x1 <- matrix(rep(1, 4), ncol = 2)
> foo(x1)
[,1] [,2]
[1,] 2 2
[2,] 2 2
# x1 after:
> x1
[,1] [,2]
[1,] 2 2
[2,] 2 2
> # Pass by value
> x2 <- matrix(rep(1, 4), ncol = 2)
> bis(x2)
[,1] [,2]
[1,] 2 2
[2,] 2 2
# x2 after:
> x2
[,1] [,2]
[1,] 1 1
[2,] 1 1 |
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Quite possibly, and that may well be true in many, many other use cases of the |
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#include <RcppArmadillo/Lightest>
// [[Rcpp::depends(RcppArmadillo)]]
// [[Rcpp::export]]
arma::mat foo(Rcpp::Nullable<Rcpp::NumericMatrix> m = R_NilValue) {
const arma::mat& x = [&m] {
if (m.isNotNull()) {
Rcpp::NumericMatrix M(m);
arma::mat x(M.begin(), M.nrow(), M.ncol(), false, true); // adv ctor, no copying
x += 1;
return x;
} else {
arma::mat x(0, 0, arma::fill::none);
return x;
}
}(); // invoke!
return x;
}
// [[Rcpp::export]]
arma::mat bar(Rcpp::Nullable<arma::mat> m = R_NilValue) {
const arma::mat& x = [&m] {
if (m.isNotNull()) {
return m.as();
} else {
return arma::mat{0, 0, arma::fill::none};
}
}(); // invoke!
return x;
}
// [[Rcpp::export]]
arma::mat bis(Rcpp::Nullable<arma::mat> m = R_NilValue) {
return (m.isNotNull() ? m.as() : arma::mat{0,0, arma::fill::none});
}
/*** R
m <- matrix(1:4, ncol = 2)
foo(NULL)
foo(m)
m
bar()
bar(m)
m
bis()
bis(m)
m
*/I still have 1:4 at the end. > Rcpp::sourceCpp("arma_nullable_example.cpp")
> m <- matrix(1:4, ncol = 2)
> foo(NULL)
<0 x 0 matrix>
> foo(m)
[,1] [,2]
[1,] 2 4
[2,] 3 5
> m
[,1] [,2]
[1,] 1 3
[2,] 2 4
> bar()
<0 x 0 matrix>
> bar(m)
[,1] [,2]
[1,] 1 3
[2,] 2 4
> m
[,1] [,2]
[1,] 1 3
[2,] 2 4
> bis()
<0 x 0 matrix>
> bis(m)
[,1] [,2]
[1,] 1 3
[2,] 2 4
> m
[,1] [,2]
[1,] 1 3
[2,] 2 4
> It works with |
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I found the gallery post on working with Nullable, but couldn't find guidance specific to scalar types (integers and doubles) or Armadillo matrices. I wanted to check if the pattern below is a recommended approach.
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