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The 4.1.0 release of simmer, the Discrete-Event Simulator for R, is on CRAN. As per request in the mailing list, now get_global() is able to work inside a generator function. Moreover, the new add_global() method attaches a global attribute to a simulator.

library(simmer)

env <- simmer()

hello_sayer <- trajectory() %>%
log_("hello world!") %>%
set_global("interarrival", 1, mod="+")

generator <- function() get_global(env, "interarrival")

env %>%
run(7) %>%
get_global("interarrival")
## 1: dummy0: hello world!
## 3: dummy1: hello world!
## 6: dummy2: hello world!
## [1] 4

Compared to plain global variables, these ones are automatically managed and thus reinitialised if the environment is reset.

env %>%
reset() %>%
get_global("interarrival")
## [1] 1
env %>%
run(7) %>%
get_global("interarrival")
## 1: dummy0: hello world!
## 3: dummy1: hello world!
## 6: dummy2: hello world!
## [1] 4

There has been a small refactoring of some parts of the C++ core, which motivates the minor version bump, but this shouldn’t be noticeable to the users. Finally, several bug fixes and improvements complete this release. See below for a complete list.

### New features:

• New getter get_selected() retrieves names of selected resources via the select() activity (#172 addressing #171).
• Source and resource getters have been vectorised to retrieve parameters from multiple entities (as part of #172).
• Simplify C++ Simulator interface for adding processes and resources (#162). The responsibility of building the objects has been moved to the caller.
• New add_global() method to attach global attributes to a simulation environment (#174 addressing #158).

### Minor changes and fixes:

• Remove 3.8.0 and 4.0.1 deprecations (#170 addressing #165).
• Fix get_global() to work outside trajectories (#170 addressing #165).
• Fix rollback() with an infinite amount (#173).
• Fix and improve schedules and managers (as part of #174).
• Fix reset() to avoid overwriting the simulation environment (#175).
Article originally published in Enchufa2.es: simmer 4.1.0.