Updated cpp_sset_range to use 'R_xlen_t' throughout and updated docum…

…entation.

R/sset.R

@@ -16,7 +16,7 @@
 #' `sset` will fall back on using `[` when no suitable method is found.
 #'
 #' To get into more detail, using `sset()` on a data frame, a new
-#' list is always allocated through `cheapr:::cpp_new_list()`.
+#' list is always allocated through `new_list()`.
 #'
 #' ### Difference to base R
 #'
@@ -25,6 +25,13 @@
 #' is not recycled, so it is good practice to make sure the logical vector
 #' matches the length of x. To return `NA` values, use `x[NA_integer_]`.
 #'
+#' ### ALTREP range subsetting
+#'
+#' When `i` is an ALTREP compact integer sequence which can be commonly created
+#' using e.g. `1:10` or using `seq_len`, `seq_along` and `seq.int`,
+#' `sset` internally uses a range-based subsetting which is faster and doesn't
+#' allocate `i` into memory.
+#'
 #' @examples
 #' library(cheapr)
 #' library(bench)

src/sset.cpp

@@ -250,7 +250,7 @@ SEXP cpp_sset_range(SEXP x, R_xlen_t from, R_xlen_t to, R_xlen_t by){
     }
     // We first switch them
     if (istart < iend){
-      int iend_temp = iend;
+      R_xlen_t iend_temp = iend;
       iend = istart;
       istart = iend_temp;
     }
@@ -393,7 +393,7 @@ case REALSXP: {
   } else {
     if (by > 0){
 #pragma omp parallel for simd num_threads(n_cores) if (do_parallel)
-      for (int i = istart - 1; i < iend; ++i){
+      for (R_xlen_t i = istart - 1; i < iend; ++i){
         p_out[i - istart + 1] = i < n ? p_x[i] : NA_REAL;
       }
     } else {
@@ -415,7 +415,7 @@ case STRSXP: {
       SET_STRING_ELT(out, k++, i < n ? p_x[i] : NA_STRING);
     }
 #pragma omp for simd
-    for (int j = istart2 - 1; j < iend2; ++j){
+    for (R_xlen_t j = istart2 - 1; j < iend2; ++j){
       SET_STRING_ELT(out, k++, j < n ? p_x[j] : NA_STRING);
     }
   } else {