R/quantify.r

In itertools2: itertools2: Functions creating iterators for efficient looping

#' Count the number of times an iterable object is TRUE
#' 
#' Returns the number of elements from an iterable object evaluate to
#' \code{TRUE}.
#' 
#' @importFrom iterators nextElem iter
#' @export
#' @param object an iterable object
#' @return the number of \code{TRUE} elements
#'
#' @examples
#' it <- iterators::iter(c(TRUE, FALSE, TRUE))
#' quantify(it) # 2
#'
#' set.seed(42)
#' x <- sample(c(TRUE, FALSE), size=10, replace=TRUE)
#' quantify(x) # Equivalent to sum(x)
#'
quantify <- function(object) {
  it <- iterators::iter(object)
  i <- 0
  repeat{
    next_elem <- try(iterators::nextElem(it), silent=TRUE)
    if (stop_iteration(next_elem)) {
      break
    }
    if (next_elem) {
      i <- i + 1
    }
  }
  i
}