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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/utils-tidy-eval.R
\name{tidyeval}
\alias{tidyeval}
\alias{expr}
\alias{enquo}
\alias{enquos}
\alias{sym}
\alias{syms}
\alias{.data}
\alias{:=}
\alias{as_name}
\alias{as_label}
\alias{quo_is_null}
\alias{quo_is_missing}
\alias{abort}
\alias{exec}
\title{Tidy eval helpers}
\description{
\itemize{
\item \code{\link[rlang:sym]{rlang::sym()}} creates a symbol from a string and
\code{\link[rlang:sym]{syms()}} creates a list of symbols from a
character vector.
\item \code{\link[rlang:topic-defuse]{enquo()}} and
\code{\link[rlang:topic-defuse]{enquos()}} delay the execution of one or
several function arguments. \code{enquo()} returns a single quoted
expression, which is like a blueprint for the delayed computation.
\code{enquos()} returns a list of such quoted expressions.
\item \code{\link[rlang:topic-defuse]{expr()}} quotes a new expression \emph{locally}. It
is mostly useful to build new expressions around arguments
captured with \code{\link[=enquo]{enquo()}} or \code{\link[=enquos]{enquos()}}:
\code{expr(mean(!!enquo(arg), na.rm = TRUE))}.
\item \code{\link[rlang:as_name]{rlang::as_name()}} transforms a quoted variable name
into a string. Supplying something else than a quoted variable
name is an error.
That's unlike \code{\link[rlang:as_label]{rlang::as_label()}} which also returns
a single string but supports any kind of R object as input,
including quoted function calls and vectors. Its purpose is to
summarise that object into a single label. That label is often
suitable as a default name.
If you don't know what a quoted expression contains (for instance
expressions captured with \code{enquo()} could be a variable
name, a call to a function, or an unquoted constant), then use
\code{as_label()}. If you know you have quoted a simple variable
name, or would like to enforce this, use \code{as_name()}.
}
To learn more about tidy eval and how to use these tools, visit
\url{https://tidyeval.tidyverse.org} and the
\href{https://adv-r.hadley.nz/metaprogramming.html}{Metaprogramming section} of
\href{https://adv-r.hadley.nz}{Advanced R}.
}
\examples{
if (FALSE) {
help("nse-defuse", package = "rlang")
}
}
\keyword{internal}
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