Added optional stop to icount. #39

Author: ramhiser

R/icount.r

@@ -12,20 +12,23 @@
 #' @param start sequence's initial value
 #' @param step sequence's step size
 #' @return sequence's iterator
-#' 
+#'
 #' @examples
 #' it <- icount()
 #' iterators::nextElem(it)
 #' iterators::nextElem(it)
 #' iterators::nextElem(it)
-#' 
+#'
 #' it2 <- icount(start=5.5, step=1.5)
 #' iterators::nextElem(it2)
 #' iterators::nextElem(it2)
 #' iterators::nextElem(it2)
-icount <- function(start=0, step=1) {
+icount <- function(start=0, step=1, stop=NULL) {
   start <- as.numeric(start)
   step <- as.numeric(step)
+  if (!is.null(stop)) {
+    stop <- as.numeric(stop)
+  }
 
   if (length(start) != 1) {
     stop("'start' must be a numeric value of length 1")
@@ -37,11 +40,15 @@ icount <- function(start=0, step=1) {
   current_val <- start - step
   nextElem <- function() {
     current_val <<- current_val + step
+
+    if (!is.null(stop) && current_val > stop) {
+      stop("StopIteration", call.=FALSE)
+    }
+
     current_val
   }
 
   it <- list(nextElem=nextElem)
   class(it) <- c("abstractiter", "iter")
   it
 }
-

man/icount.Rd

@@ -4,7 +4,7 @@
 \alias{icount}
 \title{Iterator of neverending numeric sequence with initial value and step size}
 \usage{
-icount(start = 0, step = 1)
+icount(start = 0, step = 1, stop = NULL)
 }
 \arguments{
 \item{start}{sequence's initial value}

tests/testthat/test-icount.r

@@ -47,3 +47,18 @@ test_that("icount works with a decimal step size", {
   i <- nextElem(it)
   expect_equal(i, 46.5)
 })
+
+test_that("icount works with the optional stop", {
+  it <- icount(stop=5)
+  expect_equal(0:5, unlist(as.list(it)))
+})
+
+test_that("icount works with a given initial value and a stop", {
+  it <- icount(start=42, stop=50)
+  expect_equal(42:50, unlist(as.list(it)))
+})
+
+test_that("icount works with a stop and decimal step size", {
+  it <- icount(start=42, step=1.5, stop=50)
+  expect_equal(seq(42, 50, by=1.5), unlist(as.list(it)))
+})