Define functions inside enclosing environment.

H.R

#' Hide non-function variables from function.
#' 
#' @param ... Named functions and function definitions.
#' @return Nothing.

H = function(...) {
  
  function_names = names(as.list(substitute((...)))[-1])
  function_defs = list(...)
  envir = parent.env(parent.frame())
  
  for(i in 1:length(function_names)) {
    environment(function_defs[[i]]) = envir
    assign(x = function_names[[i]], 
           value = function_defs[[i]], 
           envir = envir)
  }

}

a = 5 
H(adder = function(x) x + 2 + a)
adder(0)
# Error in adder(0) : object 'a' not found

H(fun1 = function(x) x + 2,
  fun2 = function(x) fun1(x) + 1)

fun2(4) 
# [1] 7