Test for a mizu Sentinel

Identity comparison against the four interned sentinel singletons — mizu_full, mizu_timeout, mizu_closed, mizu_peer_gone — that the verbs of mizu return to tag terminal states. inherits(x, "mizu_sentinel") tests the class alone, which any payload can carry. This includes a genuine sentinel forwarded over a channel, which arrives as an ordinary copy. mizu_is_sentinel() is provenance: TRUE only for the exact objects that the own calls of mizu return in this process. So code that relays untrusted values can distinguish its terminal states from look-alike payloads.

Usage

mizu_is_sentinel(x)

Arguments

x

any R object.

Value

TRUE or FALSE.

Details

Sentinels are ordinary values, not R conditions: nothing is signalled, and condition handlers never see them.

Examples

mizu_is_sentinel(42)
#> [1] FALSE
# class alone does not make a sentinel:
mizu_is_sentinel(structure("x", class = c("mizu_timeout", "mizu_sentinel")))
#> [1] FALSE