Fix for #501 proposed by @kevinushey

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,8 @@
+2026-02-19  Dirk Eddelbuettel  <edd@debian.org>
+
+	* inst/include/current/armadillo_bits/subview_meat.hpp: Cover special
+	case of empty subview (by Kevin)
+
 2026-01-07  Dirk Eddelbuettel  <edd@debian.org>
 
 	* .github/workflows/ci.yaml: Switch to actions/checkout@v6

inst/include/current/armadillo_bits/subview_meat.hpp

@@ -1594,7 +1594,8 @@ subview<eT>::extract(Mat<eT>& out, const subview<eT>& in)
   const uword n_cols = in.n_cols;  // number of columns in the subview
 
   arma_debug_print(arma_str::format("out.n_rows: %u; out.n_cols: %u; in.m.n_rows: %u; in.m.n_cols: %u") % out.n_rows % out.n_cols % in.m.n_rows % in.m.n_cols );
-  
+
+  if(in.n_elem == 0) { return; }
 
   if(in.is_vec())
     {
@@ -1662,6 +1663,8 @@ subview<eT>::plus_inplace(Mat<eT>& out, const subview<eT>& in)
   arma_debug_sigprint();
 
   arma_conform_assert_same_size(out, in, "addition");
+
+  if(in.n_elem == 0) { return; }
 
   const uword n_rows = in.n_rows;
   const uword n_cols = in.n_cols;
@@ -1710,6 +1713,8 @@ subview<eT>::minus_inplace(Mat<eT>& out, const subview<eT>& in)
   arma_debug_sigprint();
 
   arma_conform_assert_same_size(out, in, "subtraction");
+
+  if(in.n_elem == 0) { return; }
 
   const uword n_rows = in.n_rows;
   const uword n_cols = in.n_cols;
@@ -1758,6 +1763,8 @@ subview<eT>::schur_inplace(Mat<eT>& out, const subview<eT>& in)
   arma_debug_sigprint();
 
   arma_conform_assert_same_size(out, in, "element-wise multiplication");
+
+  if(in.n_elem == 0) { return; }
 
   const uword n_rows = in.n_rows;
   const uword n_cols = in.n_cols;
@@ -1806,6 +1813,8 @@ subview<eT>::div_inplace(Mat<eT>& out, const subview<eT>& in)
   arma_debug_sigprint();
 
   arma_conform_assert_same_size(out, in, "element-wise division");
+
+  if(in.n_elem == 0) { return; }
 
   const uword n_rows = in.n_rows;
   const uword n_cols = in.n_cols;