Hi All, I am confused about the following code. I thought that the
problem stemmed from lazy evaluation and the fact that 'i' is never
evaluated within the first lapply. However, I am then confused as to
why it gets bound to the final element of the lapply. The environments
of the returned functions are indeed different in both cases and each
environment has a local binding for 'i' it just happens to be 3 --
which I will say is wrong, but I await reeducation.
I looked for documentation concerning this, but I wasn't able to find
anything -- I imagine that this must be documented somewhere as it
appears like a reasonable thing to do. Thank you as always for any
insight. -- jim
## doesn't do what I think it should
x <- lapply(1:3, function(i) {
function() { i^2 }
})
sapply(1:3, function(i) x[[i]]())
[1] 9 9 9
## does what I expect
x <- lapply(1:3, function(i) {
print(i)
function() { i^2 }
})
[1] 1
[1] 2
[1] 3
sapply(1:3, function(i) x[[i]]())
[1] 1 4 9
> sessionInfo()
R version 2.7.1 Patched (2008-07-20 r46088)
i386-apple-darwin9.4.0
locale:
en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
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