为什么E(g)不等于它本身

Question

考虑：

library(igraph)
g <- make_ring(3)

identical(g, g)    # TRUE as expected
# [1] TRUE

dput(E(g))
# structure(1:3, is_all = TRUE, class = "igraph.es", env = <weak reference>, graph = "4f82a4da-3975-11ef-8958-675a79d1d14f")


E(g) == E(g)              # test equality.
# [1] TRUE TRUE TRUE

all.equal(E(g), E(g))     # Next try.     
# [1] TRUE

identical(E(g), E(g), ignore.environment = FALSE) # Expecting TRUE.
# [1] FALSE

identical(E(g), E(g), ignore.environment = TRUE) # Expecting TRUE.
# [1] FALSE

问题：为什么是假的？

Answer 1

我推测

identical

会给出

False

，因为

E(g)

在第一次和第二次调用之间被分配了不同的地址，例如

> library(data.table)

> address(E(g))
[1] "000001a51697f368"

> address(E(g))
[1] "000001a516666e68"