Add sparse character

NAMESPACE

@@ -1,13 +1,16 @@
 # Generated by roxygen2: do not edit by hand
 
+export(as_sparse_character)
 export(as_sparse_double)
 export(as_sparse_integer)
 export(coerce_to_sparse_data_frame)
 export(coerce_to_sparse_matrix)
 export(coerce_to_sparse_tibble)
+export(is_sparse_character)
 export(is_sparse_double)
 export(is_sparse_integer)
 export(is_sparse_vector)
+export(sparse_character)
 export(sparse_default)
 export(sparse_double)
 export(sparse_integer)

R/coerce-vector.R

@@ -41,7 +41,7 @@ as_sparse_double <- function(x, default = 0) {
 
 #' @rdname coerce-vector
 #' @export
-as_sparse_integer <- function(x, default = 0) {
+as_sparse_integer <- function(x, default = 0L) {
   if (is_sparse_integer(x)) {
     return(x)
   }
@@ -60,4 +60,26 @@ as_sparse_integer <- function(x, default = 0) {
     length = length(x),
     default = default
   )
+}
+
+#' @rdname coerce-vector
+#' @export
+as_sparse_character <- function(x, default = "") {
+  if (is_sparse_character(x)) {
+    return(x)
+  }
+
+  check_string(default)
+
+  values <- vctrs::vec_cast(x, character())
+  default <- vctrs::vec_cast(default, character())
+
+  index <- which(x != default | is.na(x))
+
+  sparse_character(
+    values = x[index],
+    positions = index,
+    length = length(x),
+    default = default
+  )
 }

R/sparse_character.R

@@ -0,0 +1,78 @@
+#' Create sparse character vector
+#' 
+#' Construction of vectors where only values and positions are recorded. The 
+#' Length and default values determine all other information.
+#' 
+#' @param values integer vector, values of non-zero entries.
+#' @param positions integer vector, indices of non-zero entries.
+#' @param length integer value, Length of vector.
+#' @param default integer value, value at indices not specified by `positions`. 
+#'   Defaults to `""`. Cannot be `NA`.
+#' 
+#' @details
+#' 
+#' `values` and `positions` are expected to be the same length, and are allowed
+#' to both have zero length.
+#' 
+#' Allowed values for `value` are character values. Missing values such as `NA` 
+#' and `NA_real_` are allowed as they are turned into `NA_character_`. 
+#' Everything else is disallowed. The values are also not allowed to take the 
+#' same value as `default`.
+#' 
+#' `positions` should be integers or integer-like doubles. Everything else is 
+#' not allowed. Positions should furthermore be positive (`0` not allowed),
+#' unique, and in increasing order. Lastly they should all be smaller that 
+#' `length`.
+#' 
+#' For developers: 
+#' 
+#' setting `options("sparsevctrs.verbose_materialize" = TRUE)` will print a 
+#' message each time a sparse vector has been forced to materialize.
+#'
+#' @seealso [sparse_double()] [sparse_integer()]
+#' 
+#' @examples
+#' sparse_character(character(), integer(), 10)
+#' 
+#' sparse_character(c("A", "C", "E"), c(2, 5, 10), 10)
+#' 
+#' str(
+#'   sparse_character(c("A", "C", "E"), c(2, 5, 10), 1000000000)
+#' )
+#' @export
+sparse_character <- function(values, positions, length, default = "") {
+  check_string(default)
+  check_number_whole(length, min = 0)
+  if (!is.integer(length)) {
+    length <- as.integer(length)
+  }
+
+  values <- vctrs::vec_cast(values, character())
+  default <- vctrs::vec_cast(default, character())
+
+  validate_positions(positions, length, len_values = length(values))
+  positions <- as.integer(positions)
+
+  if (any(values == default, na.rm = TRUE)) {
+    offenders <- which(values == default)
+    cli::cli_abort(
+      c(
+        x = "{.arg values} value must not be equal to the default {default}.",
+        i = "{default} values at index: {offenders}."
+      )
+    )
+  }
+
+  new_sparse_character(values, positions, length, default)
+}
+
+new_sparse_character <- function(values, positions, length, default) {
+  x <- list(
+    val = values,
+    pos = positions,
+    len = length,
+    default = default
+  )
+
+  .Call(ffi_altrep_new_sparse_string, x)
+}

R/sparse_double.R

@@ -29,7 +29,7 @@
 #' setting `options("sparsevctrs.verbose_materialize" = TRUE)` will print a 
 #' message each time a sparse vector has been forced to materialize.
 #'
-#' @seealso [sparse_integer()]
+#' @seealso [sparse_integer()] [sparse_character()]
 #'  
 #' @examples
 #' sparse_double(numeric(), integer(), 10)

R/sparse_integer.R

@@ -30,7 +30,7 @@
 #' setting `options("sparsevctrs.verbose_materialize" = TRUE)` will print a 
 #' message each time a sparse vector has been forced to materialize.
 #'
-#' @seealso [sparse_double()]
+#' @seealso [sparse_double()] [sparse_character()]
 #' 
 #' @examples
 #' sparse_integer(integer(), integer(), 10)
@@ -41,7 +41,7 @@
 #'   sparse_integer(c(4, 5, 7), c(2, 5, 10), 1000000000)
 #' )
 #' @export
-sparse_integer <- function(values, positions, length, default = 0) {
+sparse_integer <- function(values, positions, length, default = 0L) {
   check_number_whole(default)
   check_number_whole(length, min = 0)
   if (!is.integer(length)) {

R/type-predicates.R

@@ -6,8 +6,9 @@
 #' 
 #' @details
 #' `is_sparse_vector()` is a general function that detects any type of sparse 
-#' vector created with this package. `is_sparse_double()` and 
-#' `is_sparse_integer()` are more specific functions that only detects the type.
+#' vector created with this package. `is_sparse_double()`, 
+#' `is_sparse_integer()`, and `is_sparse_character()` are more specific 
+#' functions that only detects the type.
 #'
 #' @examples
 #' x_sparse <- sparse_double(c(pi, 5, 0.1), c(2, 5, 10), 10)
@@ -19,6 +20,9 @@
 #' is_sparse_double(x_sparse)
 #' is_sparse_double(x_dense)
 #' 
+#' is_sparse_character(x_sparse)
+#' is_sparse_character(x_dense)
+#' 
 #' # Forced materialization
 #' is_sparse_vector(x_sparse[])
 #' @name type-predicates
@@ -34,7 +38,13 @@ is_sparse_vector <- function(x) {
 
   res <- as.character(res[[1]])
 
-  res %in% c("altrep_sparse_double", "altrep_sparse_integer")
+  valid <- c(
+    "altrep_sparse_double", 
+    "altrep_sparse_integer", 
+    "altrep_sparse_string"
+  )
+
+  res %in% valid
 }
 
 #' @rdname type-predicates
@@ -62,3 +72,16 @@ is_sparse_integer <- function(x) {
 
   res == "altrep_sparse_integer"
 }
+
+#' @rdname type-predicates
+#' @export
+is_sparse_character <- function(x) {
+  res <- .Call(ffi_extract_altrep_class, x)
+  if (is.null(res)) {
+    return(FALSE)
+  }
+
+  res <- as.character(res[[1]])
+
+  res == "altrep_sparse_string"
+}

_pkgdown.yml

@@ -7,6 +7,7 @@ reference:
     contents:
     - sparse_double
     - sparse_integer
+    - sparse_character
 
   - title: Convertion functions
     contents: