new_quosure()wraps any R object (including expressions, formulas, or other quosures) into a quosure.as_quosure()is similar but it does not rewrap formulas and quosures.
Usage
new_quosure(expr, env = caller_env())
as_quosure(x, env = NULL)
is_quosure(x)Arguments
- expr
An expression to wrap in a quosure.
- env
The environment in which the expression should be evaluated. Only used for symbols and calls. This should normally be the environment in which the expression was created.
- x
An object to test.
See also
enquo()andquo()for creating a quosure by argument defusal.
Examples
# `new_quosure()` creates a quosure from its components. These are
# equivalent:
new_quosure(quote(foo), current_env())
#> <quosure>
#> expr: ^foo
#> env: 0x556760e56c40
quo(foo)
#> <quosure>
#> expr: ^foo
#> env: 0x556760e56c40
# `new_quosure()` always rewraps its input into a new quosure, even
# if the input is itself a quosure:
new_quosure(quo(foo))
#> <quosure>
#> expr: ^<quosure>
#> env: 0x556760e56c40
# This is unlike `as_quosure()` which preserves its input if it's
# already a quosure:
as_quosure(quo(foo))
#> <quosure>
#> expr: ^foo
#> env: 0x556760e56c40
# `as_quosure()` uses the supplied environment with naked expressions:
env <- env(var = "thing")
as_quosure(quote(var), env)
#> <quosure>
#> expr: ^var
#> env: 0x5567616cb7b0
# If the expression already carries an environment, this
# environment is preserved. This is the case for formulas and
# quosures:
as_quosure(~foo, env)
#> <quosure>
#> expr: ^foo
#> env: 0x556760e56c40
as_quosure(~foo)
#> <quosure>
#> expr: ^foo
#> env: 0x556760e56c40
# An environment must be supplied when the input is a naked
# expression:
try(
as_quosure(quote(var))
)
#> Warning: `as_quosure()` requires an explicit environment as of rlang 0.3.0. Please
#> supply `env`.
#> This warning is displayed once every 8 hours.
#> <quosure>
#> expr: ^var
#> env: 0x556760e56c40