The 4.0.1 release of simmer, the Discrete-Event Simulator for R, is on CRAN since a couple of weeks ago. There are few changes, notably new getters (get_sources(), get_resources(), get_trajectory()) for simmer environments and some improvements in resource selection policies (see details in help(select)).

A new convenience function, when_activated, makes it easier to generate arrivals on demand, triggered from trajectories. Let us consider, for instance, a simple restocking pattern:

library(simmer)

restock <- trajectory() %>%
  log_("restock")

serve <- trajectory() %>%
  log_("serve") %>%
  activate("Restock")

env <- simmer() %>%
  add_generator("Customer", serve, at(1, 2, 3)) %>%
  add_generator("Restock", restock, when_activated()) %>%
  run()
## 1: Customer0: serve
## 1: Restock0: restock
## 2: Customer1: serve
## 2: Restock1: restock
## 3: Customer2: serve
## 3: Restock2: restock

Finally, this release leverages the new fast evaluation framework offered by Rcpp (>= 0.12.18) by default, and includes some minor improvements and bug fixes.