r/R/scalar.R

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#' @include arrow-datum.R

#' @title Arrow scalars
#' @usage NULL
#' @format NULL
#' @docType class
#'
#' @description A `Scalar` holds a single value of an Arrow type.
#'
#' @name Scalar
#' @rdname Scalar
#' @export
Scalar <- R6Class("Scalar",
  inherit = ArrowDatum,
  # TODO: document the methods
  public = list(
    ToString = function() Scalar__ToString(self),
    as_vector = function() Scalar__as_vector(self),
    as_array = function() MakeArrayFromScalar(self),
    Equals = function(other, ...) {
      inherits(other, "Scalar") && Scalar__Equals(self, other)
    },
    ApproxEquals = function(other, ...) {
      inherits(other, "Scalar") && Scalar__ApproxEquals(self, other)
    }
  ),
  active = list(
    is_valid = function() Scalar__is_valid(self),
    null_count = function() sum(!self$is_valid),
    type = function() Scalar__type(self)
  )
)
Scalar$create <- function(x, type = NULL) {
  if (is.null(x)) {
    x <- vctrs::unspecified(1)
  } else if (length(x) != 1 && !is.data.frame(x)) {
    # Wrap in a list type
    x <- list(x)
  }
  Array__GetScalar(Array$create(x, type = type), 0)
}

#' @rdname array
#' @usage NULL
#' @format NULL
#' @export
StructScalar <- R6Class("StructScalar",
  inherit = Scalar,
  public = list(
    field = function(i) StructScalar__field(self, i),
    GetFieldByName = function(name) StructScalar__GetFieldByName(self, name)
  )
)

#' @export
length.Scalar <- function(x) 1L

#' @export
is.na.Scalar <- function(x) !x$is_valid

#' @export
sort.Scalar <- function(x, decreasing = FALSE, ...) x