quo-predicates {rlang} | R Documentation |
These functions examine the expression of a quosure with a predicate.
quo_is_missing(quo) quo_is_symbol(quo) quo_is_lang(quo) quo_is_symbolic(quo) quo_is_null(quo)
quo |
A quosure. |
When missing arguments are captured as quosures, either through
enquo()
or quos()
, they are returned as an empty quosure. These
quosures contain the missing argument and typically
have the empty environment as enclosure.
quo_is_symbol(quo(sym)) quo_is_symbol(quo(foo(bar))) # You can create empty quosures by calling quo() without input: quo <- quo() quo_is_missing(quo) is_missing(f_rhs(quo))