Base R method

• Base R methods do not support unquoting.

• Base R equivalent of expr is quote

• Base R equivalent of enexpr is substitute (note that enexpr uses substitute!)

enexpr
#>function (arg) 
#>{
#>    .Call(ffi_enexpr, substitute(arg), parent.frame())
#>}

• bquote() provides a limited form of quasiquotation, see section 19.5

• ~, the formula, is a quoting function, discussed in Section 20.3.4