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Understanding environments and frames
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| # What you need to know: | |
| # * environments -- inheritance of definition | |
| # * frames -- call reference | |
| # | |
| # What does that mean? | |
| # * environments are inherited when a function is defined (i.e. f <- function () {}) | |
| # * frames refer to where a function was called from, not where it was defined | |
| i <- 1 | |
| # This demonstrates environment inheritance | |
| f1 <- function (x) { | |
| print(exists("i")) | |
| print(parent.env(environment())) | |
| j <- 2 | |
| function (y) { | |
| print(exists("j")) | |
| print(parent.env(environment())) | |
| k <- 3 | |
| function (z) { | |
| print(exists("k")) | |
| print(parent.env(environment())) | |
| ls() | |
| } | |
| } | |
| } | |
| f2 <- f1(10) | |
| f3 <- f2(100) | |
| # This demonstrates the call stack | |
| f1 <- function (x) { | |
| print(exists("i")) | |
| print(sys.parent()) # <-- 0 | |
| (function() {print(sys.parent())})() # <-- 1 | |
| j <- 2 | |
| function (y) { | |
| print(exists("j")) | |
| print(sys.parent(2)) # <-- 0 | |
| k <- 3 | |
| function (z) { | |
| print(exists("k")) | |
| print(sys.parent(3)) # <-- 0 | |
| ls() | |
| } | |
| } | |
| } | |
| f2 <- f1(10) | |
| f3 <- f2(100) |
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