quo-predicates

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Is a quosure quoting a symbolic, missing or NULL object?

These functions examine the expression of a quosure with a predicate.

Usage
quo_is_missing(quo)

quo_is_symbol(quo)

quo_is_lang(quo)

quo_is_symbolic(quo)

quo_is_null(quo)

Arguments
quo

A quosure.

Empty quosures

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.

Aliases
  • quo-predicates
  • quo_is_missing
  • quo_is_symbol
  • quo_is_lang
  • quo_is_symbolic
  • quo_is_null
Examples
# NOT RUN {
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))
# }
Documentation reproduced from package rlang, version 0.1.6, License: GPL-3

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