Lunch & Learn 07/30/17: R environments

lunchnlearn-073017.md

env <- new.env()

d <- 1
fn <- function(a, b) {
  a + b + d
}

fn2 <- (function() {
  d <- 2
  function(a, b) {
    a + b + d
  }
})()
environment(fn2)

# function: (formal_parameters, body, environment)

function(a, b) { c; d }
`function`(alist(a=, b=), quote({ c; d }), GlobalEnv())

formals(fn)
body(fn)
environment(fn)

environment(fn2)$d <- 3
fn2(1, 2)

# fn2 gets it values from environment(fn2)
# if d is present in environment(fn2), it gets taken from there
# otherwise, we traverse the "parent environment chain"
rm("d", envir = environment(fn2))

fn4 <- function(a, d) {
  a + d
}

fn3 <- local({
  local({
    d <- 5
    local({
      d <- 1
      local({
        function(a, b) {
          a + b + d
        }
      })
    })
  })
})

search() # gives you the package search path

# Within packages, local variables and functions are 
# found from:
# function environment, package namespace, imports namespace,
# copy of base, global env

env <- new.env()
env$d <- 8
makeActiveBinding("d", function() env$d, env = environment(fn3))

F <- function(a, b) {
  browser()
  a + b
}

G <- local({
  d <- 5
  function() {
    F(1, 2)
  }
})

H <- local({
  G()
})

Z <- 
  (function(){
    print("1")
    print(environment())
    (function(){
      print("2")
      print(environment())
      (function(){
        print("3")
        print(environment())
        print(parent.env(environment()))
        print(parent.env(parent.env(environment())))
        print(parent.frame())
        print(parent.frame(2))
        print(parent.frame(3))
        print(parent.frame(4))
        print(parent.frame(5))
        stop("error")
      })()
    })()
  })()

big_fn <- local({ function(a, b) {
  a + b
} })