use tail for check (#802)

* use `tail` for check

* add news item

* add regression test

NEWS.md

@@ -23,7 +23,7 @@ A release that introduces model improvements to the Gaussian Process models, alo
 - Switch to broadcasting from random walks and added unit tests. By @seabbs in #747 and reviewed by @jamesmbaazam.
 - Optimised convolution code to take into account the relative length of the vectors being convolved. See #745 by @seabbs and reviewed by @jamesmbaazam.
 - Switch to broadcasting the day of the week effect. By @seabbs in #746 and reviewed by @jamesmbaazam.
-- A warning is now thrown if nonparametric PMFs passed to delay options have consecutive tail values that are below a certain low threshold as these lead to loss in speed with little gain in accuracy. By @jamesmbaazam in #752 and reviewed by @seabbs.
+- A warning is now thrown if nonparametric PMFs passed to delay options have consecutive tail values that are below a certain low threshold as these lead to loss in speed with little gain in accuracy. By @jamesmbaazam in #752 and reviewed by @seabbs, with a subsequent bug fix in #802.
 - `dist_fit()` can now accept any number of `samples` without throwing a warning when `samples` < 1000 in #751 by @jamesmbaazam and reviewed by @seabbs and @sbfnk.
 
 ## Package changes

R/checks.R

@@ -132,7 +132,7 @@ check_stan_delay <- function(dist) {
 #' @return Called for its side effects.
 #' @keywords internal
 check_sparse_pmf_tail <- function(pmf, span = 5, tol = 1e-6) {
-  if (all(pmf[(length(pmf) - span + 1):length(pmf)] < tol)) {
+  if (all(tail(pmf, span) < tol)) {
     cli_warn(
       c(
         "!" = "The PMF tail has {col_blue(span)} consecutive value{?s} smaller

tests/testthat/test-delays.R

@@ -63,6 +63,13 @@ test_that("delay parameters can be specified in different ways", {
     ), digits = 2), n = -2),
     c(0.08, 0.33, 0.36, 0.16, 0.05, 0.02, 0.01, 0.00, 0.00, 1.00)
   )
+  expect_equal(
+    test_stan_delays(
+      delays = delay_opts(NonParametric(pmf = c(0.1, 0.6, 0.3))),
+      params = delay_params
+    ),
+    c(0.0, 1.0, 0.1, 0.6, 0.3, 1.0)
+  )
 })
 
 test_that("truncation parameters can be specified in different ways", {