Explain a lazy evaluation quirk

by

This is no longer true as of R 3.2.0!

The corresponding line in the change log reads:

Higher order functions such as the apply functions and Reduce() now
force arguments to the functions they apply in order to eliminate
undesirable interactions between lazy evaluation and variable capture
in closures.

And indeed:

add <- function(x) {
  function(y) x + y
}
adders <- lapply(1:10, add)
adders[[1]](10)
# [1] 11
adders[[10]](10)
# [1] 20

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