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% File src/library/base/man/call.Rd
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% File src/library/base/man/call.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2018 R Core Team
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% Copyright 1995-2019 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{call}
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\name{call}
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\title{Function Calls}
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\alias{call}
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\alias{call}
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\alias{is.call}
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\alias{is.call}
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\alias{as.call}
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\alias{as.call}
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\title{Function Calls}
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\description{
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\description{
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Create or test for objects of \code{\link{mode}} \code{"call"} (or
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Create or test for objects of \code{\link{mode}} \code{"call"} (or
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\code{"("}, see Details).
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\code{"("}, see Details).
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}
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}
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\usage{
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\usage{
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\item{name}{a non-empty character string naming the function to be called.}
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\item{name}{a non-empty character string naming the function to be called.}
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\item{\dots}{arguments to be part of the call.}
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\item{\dots}{arguments to be part of the call.}
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\item{x}{an arbitrary \R object.}
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\item{x}{an arbitrary \R object.}
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}
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}
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\details{
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\details{
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\describe{
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\code{call} returns an unevaluated function call, that is, an
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\item{\code{call} }{returns an unevaluated function call, that is, an
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unevaluated expression which consists of the named function applied to
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unevaluated expression which consists of the named function applied to
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the given arguments (\code{name} must be a quoted string which gives
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the given arguments (\code{name} must be a quoted string which gives
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the name of a function to be called). Note that although the call is
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the name of a function to be called). Note that although the call is
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unevaluated, the arguments \code{\dots} are evaluated.
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unevaluated, the arguments \code{\dots} are evaluated.
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\code{call} is a primitive, so the first argument is
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\code{call} is a primitive, so the first argument is
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taken as \code{name} and the remaining arguments as arguments for the
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taken as \code{name} and the remaining arguments as arguments for the
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constructed call: if the first argument is named the name must
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constructed call: if the first argument is named the name must
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partially match \code{name}.
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partially match \code{name}.
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}
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\item{\code{is.call} }{is used to determine whether \code{x} is a call (i.e.,
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of mode \code{"call"} or \code{"("}). Note that
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\itemize{
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\item{\code{is.call(x)} is strictly equivalent to
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\code{typeof(x) == "language"}.}
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\item{\code{\link{is.language}()} is also true for calls (but also
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for \code{\link{symbol}}s and \code{\link{expression}}s where
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\code{is.call()} is false).}
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}
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}
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\item{\code{as.call(x)}: }{Objects of mode \code{"list"} can be coerced to mode \code{"call"}.
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The first element of the list becomes the function part of the call,
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so should be a function or the name of one (as a symbol; a quoted
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string will not do).
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\code{is.call} is used to determine whether \code{x} is a call (i.e.,
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of mode \code{"call"} or \code{"("}). Note that
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If you think of using \code{as.call(<string>)}, consider using
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\itemize{
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\item{\code{is.call(x)} is strictly equivalent to
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\code{\link{str2lang}(*)} which is an efficient version of
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\code{typeof(x) == "language"}.}
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\code{\link{parse}(text=*)}.
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\item{\code{\link{is.language}()} is also true for calls (but also
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Note that \code{\link{call}()} and \code{\link{as.call}()}, when
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for \code{\link{symbol}}s and \code{\link{expression}}s where
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applicable, are much preferable to these \code{\link{parse}()} based
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\code{is.call()} is false).}
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approaches.
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}
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}
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}
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Objects of mode \code{"list"} can be coerced to mode \code{"call"}.
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The first element of the list becomes the function part of the call,
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so should be a function or the name of one (as a symbol; a quoted
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string will not do).
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All three are \link{primitive} functions.
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All three are \link{primitive} functions.
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}
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}
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\section{Warning}{
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\section{Warning}{
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\code{call} should not be used to attempt to evade restrictions on the
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\code{call} should not be used to attempt to evade restrictions on the
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use of \code{.Internal} and other non-API calls.
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use of \code{.Internal} and other non-API calls.
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\code{\link{Recall}} for recursive calling of functions;
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\code{\link{Recall}} for recursive calling of functions;
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further
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further
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\code{\link{is.language}},
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\code{\link{is.language}},
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\code{\link{expression}},
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\code{\link{expression}},
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\code{\link{function}}.
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\code{\link{function}}.
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Producing \code{\link{call}}s etc from character: \code{\link{str2lang}} and
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\code{\link{parse}}.
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}
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}
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\references{
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\references{
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Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
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Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
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\emph{The New S Language}.
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\emph{The New S Language}.
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Wadsworth & Brooks/Cole.
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Wadsworth & Brooks/Cole.
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The R Project SVN
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