Quosure objects wrap an expression with a lexical enclosure. This is a powerful quoting (see base::quote() and quo()) mechanism that makes it possible to carry and manipulate expressions while making sure that its symbolic content (symbols and named calls, see is_symbolic()) is correctly looked up during evaluation.

  • new_quosure() creates a quosure from a raw expression and an environment.

  • as_quosure() is useful for functions that expect quosures but allow specifying a raw expression as well. It has two possible effects: if x is not a quosure, it wraps it into a quosure bundling env as scope. If x is an unscoped quosure (see is_quosure()), env is used as a default scope. On the other hand if x has a valid enclosure, it is returned as is (even if env is not the same as the formula environment).

  • While as_quosure() always returns a quosure (a one-sided formula), even when its input is a formula or a definition, as_quosureish() returns quosureish inputs as is.

as_quosure(x, env = caller_env())

as_quosureish(x, env = caller_env())

Arguments

x

An object to convert.

env

An environment specifying the lexical enclosure of the quosure.

See also

is_quosure()

Examples

# Sometimes you get unscoped formulas because of quotation: f <- ~~expr inner_f <- f_rhs(f) str(inner_f)
#> language ~expr
is_quosureish(inner_f, scoped = TRUE)
#> [1] FALSE
# You can use as_quosure() to provide a default environment: as_quosure(inner_f, base_env())
#> <quosure: base> #> ~~expr
# Or convert expressions or any R object to a validly scoped quosure: as_quosure(quote(expr), base_env())
#> <quosure: base> #> ~expr
as_quosure(10L, base_env())
#> <quosure: empty> #> ~10L
# While as_quosure() always returns a quosure (one-sided formula), # as_quosureish() returns quosureish objects: as_quosure(a := b)
#> <quosure: local> #> ~`:=`(a, b)
as_quosureish(a := b)
#> <quosure: local> #> ~`:=`(a, b)
as_quosureish(10L)
#> <quosure: local> #> ~10L