问一元运算符重载:风险？

EN

# function to overload "!" for one purpose only
#this is adapted  from the sos package code for "???", credited to Duncan Murdoch.
# Example of how to create a specialized unary  operator that doesn't require
# parentheses for its argument.  So far as I can tell,  
#the only way to do this is to overload an existing function or
# operator which doesn't require parentheses.  "?" and "!" meet this requirement.
`!` <- function (e1, e2)  { 
call <- match.call()
#  match.call breaks out each callable function in argument list (which was "??foo" for the sos package "???",
 #  which allows topicExpr1 to become  a list variable w/ callable function "!"  (or "?" in sos) 
original <- function() { 
    call[[1]]<-quote(base::`!`)
    return(eval(call, parent.frame(2)))
}

   # this does preclude my ever having an actual
   # variable called "newdev" (or at least trying to create the actual NOT of it) 
if(call[[2]] =='newdev') {
    windows(4.5,4.5,restoreConsole=T)
}else{
    return(original())  # do what "!" is supposed to do 
}
}